The medical discoveries of the past 1,000 years have saved countless lives and have doubled the life expectancy of people in many parts of the world. In this October 1999 Encarta Yearbook article, physicians Meyer Friedman and Gerald W. Friedland explore ten discoveries that fundamentally changed the way scientists and physicians were able to improve human health.
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Sunday, July 6, 2008
The Greatest Medical Discoveries of the Millennium
By Meyer Friedman and Gerald W. Friedland
During the last 1,000 years, a series of monumental discoveries revolutionized the practice of medicine. These discoveries have saved millions of lives and brought about remarkable improvements in the health of entire populations.
One thousand years ago the average person in Europe could expect to live about 30 years. Of 100 children born alive, 40 would die before their first birthday. Disease and infections, largely the result of squalid living conditions, claimed untold numbers of lives. The average life span throughout the industrialized West has now more than doubled the average in 1000—to about 76.5 years for babies born in 1997 in the United States. Infant mortality rates are now a mere fraction of what they were 1,000 years ago.
Medical breakthroughs during the next millennium will probably bring even longer, healthier lives. Advances in genetics, for example, offer hope of new treatments to cure serious diseases such as cancer, eliminate genetic defects from families, and possibly even slow the aging process. And recent developments in transplantation technology suggest that soon it may be possible to grow replacement organs in the laboratory. But none of these anticipated breakthroughs would be possible—even thinkable—without the pioneering medical discoveries of the last 1,000 years.
Sorting through literally thousands of medical discoveries made during the past millennium to determine the ten most important is a challenge. How is the significance of a discovery measured? One factor is paramount: The most fundamental breakthroughs led to multiple other discoveries that eventually reshaped medicine and affected millions, even billions, of people. To be sure, changes in medical practices often lagged far behind the initial discovery; effective therapies sometimes emerged only after many years. These discoveries have attained the status of millennial importance not because they quickly helped physicians save lives, but because they fundamentally shifted the way scientists and physicians thought about human health. In so doing, the discoveries opened vast new fields of research that would revolutionize medicine and save the lives of incalculable numbers of people.
These seminal breakthroughs are, in the order of their discovery, human anatomy, circulation of blood, bacteria, vaccination, surgical anesthesia, X rays, blood typing, tissue culture, antibiotics, and the structure of deoxyribonucleic acid (DNA).
source: encarta encyclopedia
By Meyer Friedman and Gerald W. Friedland
During the last 1,000 years, a series of monumental discoveries revolutionized the practice of medicine. These discoveries have saved millions of lives and brought about remarkable improvements in the health of entire populations.
One thousand years ago the average person in Europe could expect to live about 30 years. Of 100 children born alive, 40 would die before their first birthday. Disease and infections, largely the result of squalid living conditions, claimed untold numbers of lives. The average life span throughout the industrialized West has now more than doubled the average in 1000—to about 76.5 years for babies born in 1997 in the United States. Infant mortality rates are now a mere fraction of what they were 1,000 years ago.
Medical breakthroughs during the next millennium will probably bring even longer, healthier lives. Advances in genetics, for example, offer hope of new treatments to cure serious diseases such as cancer, eliminate genetic defects from families, and possibly even slow the aging process. And recent developments in transplantation technology suggest that soon it may be possible to grow replacement organs in the laboratory. But none of these anticipated breakthroughs would be possible—even thinkable—without the pioneering medical discoveries of the last 1,000 years.
Sorting through literally thousands of medical discoveries made during the past millennium to determine the ten most important is a challenge. How is the significance of a discovery measured? One factor is paramount: The most fundamental breakthroughs led to multiple other discoveries that eventually reshaped medicine and affected millions, even billions, of people. To be sure, changes in medical practices often lagged far behind the initial discovery; effective therapies sometimes emerged only after many years. These discoveries have attained the status of millennial importance not because they quickly helped physicians save lives, but because they fundamentally shifted the way scientists and physicians thought about human health. In so doing, the discoveries opened vast new fields of research that would revolutionize medicine and save the lives of incalculable numbers of people.
These seminal breakthroughs are, in the order of their discovery, human anatomy, circulation of blood, bacteria, vaccination, surgical anesthesia, X rays, blood typing, tissue culture, antibiotics, and the structure of deoxyribonucleic acid (DNA).
source: encarta encyclopedia
Setting the Stage
The practice of medicine is as old as civilization itself, but the Greeks are generally credited with inventing the science of medicine—using observation and experience rather than appeals to supernatural forces to treat disease. Although Greek medical knowledge was passed on to the conquering Romans, it fell into obscurity as the Roman Empire collapsed in the early Middle Ages.
A period of stagnation in the sciences, combined with sporadic epidemics of the bubonic plague, smallpox, and other diseases, reinforced the turn toward superstition and magical treatments in medieval Europe. Only fragments of the ancient medical learning survived. Many people viewed disease as a form of punishment for sins or as the result of demonic forces. Prayer was a standard form of treatment.
Western medicine received a major boost when the Italian universities of Salerno, Bologna, and Padua established medical faculties in the 9th and 10th centuries. By the 12th century, the University of Paris in France and Oxford University in England had also founded faculties of medicine. These institutions provided facilities for research, set examination requirements for graduating physicians, and laid the foundations for the extraordinary revival of Western medicine in the 16th and 17th centuries—a revival that has continued to this day.
source: encarta encyclopedia
The practice of medicine is as old as civilization itself, but the Greeks are generally credited with inventing the science of medicine—using observation and experience rather than appeals to supernatural forces to treat disease. Although Greek medical knowledge was passed on to the conquering Romans, it fell into obscurity as the Roman Empire collapsed in the early Middle Ages.
A period of stagnation in the sciences, combined with sporadic epidemics of the bubonic plague, smallpox, and other diseases, reinforced the turn toward superstition and magical treatments in medieval Europe. Only fragments of the ancient medical learning survived. Many people viewed disease as a form of punishment for sins or as the result of demonic forces. Prayer was a standard form of treatment.
Western medicine received a major boost when the Italian universities of Salerno, Bologna, and Padua established medical faculties in the 9th and 10th centuries. By the 12th century, the University of Paris in France and Oxford University in England had also founded faculties of medicine. These institutions provided facilities for research, set examination requirements for graduating physicians, and laid the foundations for the extraordinary revival of Western medicine in the 16th and 17th centuries—a revival that has continued to this day.
source: encarta encyclopedia
Human Anatomy
Before modern medical science could emerge, medical practitioners needed an accurate understanding of human anatomy. Without clear descriptions of the structure of the human body, it was impossible to learn what different bodily parts actually do. Once researchers understood how parts of the body worked, they were better able to devise medical therapies to restore proper functions.
Amazingly, no one knew much about human anatomy until 1543, when the Belgian anatomist Andreas Vesalius wrote De Humani Corporis Fabrica, Libri Septem (On the Structure of the Human Body, in Seven Books). For centuries, exploration of the anatomy of human corpses was forbidden. In medieval Europe, knowledge about anatomy was based largely on the teachings of the Roman physician Galen (129-199?). Galen's anatomical descriptions were based on dissections of animals, which differ in many ways from humans. But contradicting Galen was dangerous because the powerful Roman Catholic Church accepted his findings as gospel. A few brave souls had tried to correct some of Galen's errors, but their work was lost for centuries.
Ambitious, driven, and ruthless, 23-year-old Vesalius received his medical degree in 1537 from the University of Padua and was immediately appointed head of surgery and anatomy there. As a student, and later as a scientist, he recovered human corpses from cemeteries late at night. He even encouraged his students to note patients who were at death's door so that he could steal their bodies for dissection before they were buried. Vesalius slept, night after night, with corpses in his own bedroom, and he hired Italy's greatest artists to draw what he found.
In 1543 Vesalius completed his seven-book masterpiece, richly illustrated with more than 200 magnificent drawings. Many consider it one of the greatest medical books ever published. This monumental work gave medicine a precious gift: For the first time, human anatomy was based on careful dissection and observation rather than on a rigid orthodoxy rooted in ancient texts.
source: encarta encyclopedia
Before modern medical science could emerge, medical practitioners needed an accurate understanding of human anatomy. Without clear descriptions of the structure of the human body, it was impossible to learn what different bodily parts actually do. Once researchers understood how parts of the body worked, they were better able to devise medical therapies to restore proper functions.
Amazingly, no one knew much about human anatomy until 1543, when the Belgian anatomist Andreas Vesalius wrote De Humani Corporis Fabrica, Libri Septem (On the Structure of the Human Body, in Seven Books). For centuries, exploration of the anatomy of human corpses was forbidden. In medieval Europe, knowledge about anatomy was based largely on the teachings of the Roman physician Galen (129-199?). Galen's anatomical descriptions were based on dissections of animals, which differ in many ways from humans. But contradicting Galen was dangerous because the powerful Roman Catholic Church accepted his findings as gospel. A few brave souls had tried to correct some of Galen's errors, but their work was lost for centuries.
Ambitious, driven, and ruthless, 23-year-old Vesalius received his medical degree in 1537 from the University of Padua and was immediately appointed head of surgery and anatomy there. As a student, and later as a scientist, he recovered human corpses from cemeteries late at night. He even encouraged his students to note patients who were at death's door so that he could steal their bodies for dissection before they were buried. Vesalius slept, night after night, with corpses in his own bedroom, and he hired Italy's greatest artists to draw what he found.
In 1543 Vesalius completed his seven-book masterpiece, richly illustrated with more than 200 magnificent drawings. Many consider it one of the greatest medical books ever published. This monumental work gave medicine a precious gift: For the first time, human anatomy was based on careful dissection and observation rather than on a rigid orthodoxy rooted in ancient texts.
source: encarta encyclopedia
Circulation of Blood
English physician William Harvey's discovery of what the heart does and how the blood circulates is widely regarded as the single greatest medical achievement of all time: It established the principle of doing experiments in medicine to learn how the body's organs and tissues function. Published in 1628, Harvey's groundbreaking book Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (Anatomical Essay on the Motion of the Heart and Blood in Animals) spurred research into the mechanical functions of many bodily processes, including respiration, digestion, metabolism, and reproduction.
Harvey received his medical degree from the University of Padua, where he learned one very important fact: Veins have valves that permit blood to travel in only one direction. However, the exact role of the valves was unclear.
Realizing that it was still dangerous to contradict Galen, who had claimed that the liver not only makes the body's blood but also pumps it through the body, Harvey decided to study blood flow by operating on live animals. For a period of 12 years Harvey conducted his experiments before members of the influential Royal College of Physicians in London, England. He wanted their support for his book, which praised Galen while challenging many of his ideas.
In the 8th chapter of his 17-chapter book, Harvey carefully introduced the revolutionary idea that blood goes in a circle in the body, traveling from the heart to the arteries to the veins and back to the heart. The next 9 chapters proved, in wonderfully clear English, that he was right.
In a series of brilliant experiments in animals and humans, Harvey demonstrated how blood circulates in the body. When an artery was blocked, the veins draining this artery collapsed. When a vein was blocked, it swelled below the blockage and collapsed above it, but the swelling disappeared when the blockage was removed. He also showed that the valves in veins allow blood to flow only in the direction of the heart. Together, these discoveries proved that blood moves in a circle in the body—that is, there is a “circulation.”
source: encarta encyclopedia
English physician William Harvey's discovery of what the heart does and how the blood circulates is widely regarded as the single greatest medical achievement of all time: It established the principle of doing experiments in medicine to learn how the body's organs and tissues function. Published in 1628, Harvey's groundbreaking book Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (Anatomical Essay on the Motion of the Heart and Blood in Animals) spurred research into the mechanical functions of many bodily processes, including respiration, digestion, metabolism, and reproduction.
Harvey received his medical degree from the University of Padua, where he learned one very important fact: Veins have valves that permit blood to travel in only one direction. However, the exact role of the valves was unclear.
Realizing that it was still dangerous to contradict Galen, who had claimed that the liver not only makes the body's blood but also pumps it through the body, Harvey decided to study blood flow by operating on live animals. For a period of 12 years Harvey conducted his experiments before members of the influential Royal College of Physicians in London, England. He wanted their support for his book, which praised Galen while challenging many of his ideas.
In the 8th chapter of his 17-chapter book, Harvey carefully introduced the revolutionary idea that blood goes in a circle in the body, traveling from the heart to the arteries to the veins and back to the heart. The next 9 chapters proved, in wonderfully clear English, that he was right.
In a series of brilliant experiments in animals and humans, Harvey demonstrated how blood circulates in the body. When an artery was blocked, the veins draining this artery collapsed. When a vein was blocked, it swelled below the blockage and collapsed above it, but the swelling disappeared when the blockage was removed. He also showed that the valves in veins allow blood to flow only in the direction of the heart. Together, these discoveries proved that blood moves in a circle in the body—that is, there is a “circulation.”
source: encarta encyclopedia
Bacteria
After the momentous medical breakthroughs of Vesalius and Harvey came the 17th-century discovery of one of the human body's greatest enemies: bacteria. This discovery eventually led to the realization that exposure to certain microorganisms could cause disease. It also prompted new theories of antiseptics that sharply lowered mortality rates from surgery.
Antoni van Leeuwenhoek, a part-time janitor and haberdasher working in Delft, Holland, discovered bacteria and other microorganisms using a microscope that he built himself. Through the influence of a friend, a Dutch physician, he was invited to write letters to the Royal Society of London—a group dedicated to the advancement of science. These letters were translated from Dutch into English and published in the society's journal Philosophical Transactions.
Leeuwenhoek's most famous letter was published on March 16, 1677. In this letter he described looking at a drop of rainwater through his microscope. The drop was taken from a tub where it had been allowed to stand for several days. To his amazement, he saw exceedingly tiny animals, known today as protozoa, swimming in the water. He also observed other equally small animals that did not move at all, now known as bacteria. No one at the Royal Society knew anything about these little creatures, which Leeuwenhoek called animalcules. At the request of the stunned members of the Royal Society, several of the most respected citizens of Delft were asked to verify Leeuwenhoek's microscopic findings. They did so, and in 1680 Leeuwenhoek was elected a fellow of the prestigious Royal Society.
Later discoveries extended the significance of Leeuwenhoek's work, especially the superb finding by the German scientist Robert Koch in 1876. Koch found that the microscopic anthrax bacillus could actually cause a fatal human disease. Until Koch's discovery, many scientists thought it absurd that microscopic creatures could harm much larger animals, such as humans. In 1882 Koch showed that another kind of bacterium, the tubercle bacillus, caused tuberculosis, a discovery for which he won the Nobel Prize in 1905.
Unlike Koch, who was a country physician when he made his epochal discoveries, the French chemist and biologist Louis Pasteur disliked physicians so much that he would not have them as workers in his laboratory. Despite his disdain for physicians, he was deeply fascinated by diseases of various kinds. Pasteur discovered that putrefaction (a decomposition of organic substances) is caused by microorganisms that float in the air. Pasteur learned that he could prevent putrefaction by subjecting organic substances to moderate but not extreme heat, a process known as pasteurization.
In 1865 Joseph Lister, an English surgeon, read of Pasteur's research on putrefaction. Lister recalled that whereas simple bone fractures invariably healed, compound fractures (bone fractures bursting the skin) almost always began to putrefy. Lister was certain that this dangerous, infectious process was caused by the wretched microorganisms that Pasteur had described. To test his theory, Lister covered his patients' compound fractures, previously exposed to the air, with linen strips soaked in carbolic acid. He believed the carbolic acid might exterminate the airborne microorganisms.
Lister treated compound fractures and open surgical wounds with carbolic acid for nine months. During this time, he did not observe a single infection in his surgical ward. The results of his experiments, published in 1867, gave rise to antiseptic surgery. Although Lister's antiseptic technique initially encountered resistance from other physicians, it soon became widely accepted, and deaths due to infections in the operating room plummeted.
source: encarta enyclopedia
After the momentous medical breakthroughs of Vesalius and Harvey came the 17th-century discovery of one of the human body's greatest enemies: bacteria. This discovery eventually led to the realization that exposure to certain microorganisms could cause disease. It also prompted new theories of antiseptics that sharply lowered mortality rates from surgery.
Antoni van Leeuwenhoek, a part-time janitor and haberdasher working in Delft, Holland, discovered bacteria and other microorganisms using a microscope that he built himself. Through the influence of a friend, a Dutch physician, he was invited to write letters to the Royal Society of London—a group dedicated to the advancement of science. These letters were translated from Dutch into English and published in the society's journal Philosophical Transactions.
Leeuwenhoek's most famous letter was published on March 16, 1677. In this letter he described looking at a drop of rainwater through his microscope. The drop was taken from a tub where it had been allowed to stand for several days. To his amazement, he saw exceedingly tiny animals, known today as protozoa, swimming in the water. He also observed other equally small animals that did not move at all, now known as bacteria. No one at the Royal Society knew anything about these little creatures, which Leeuwenhoek called animalcules. At the request of the stunned members of the Royal Society, several of the most respected citizens of Delft were asked to verify Leeuwenhoek's microscopic findings. They did so, and in 1680 Leeuwenhoek was elected a fellow of the prestigious Royal Society.
Later discoveries extended the significance of Leeuwenhoek's work, especially the superb finding by the German scientist Robert Koch in 1876. Koch found that the microscopic anthrax bacillus could actually cause a fatal human disease. Until Koch's discovery, many scientists thought it absurd that microscopic creatures could harm much larger animals, such as humans. In 1882 Koch showed that another kind of bacterium, the tubercle bacillus, caused tuberculosis, a discovery for which he won the Nobel Prize in 1905.
Unlike Koch, who was a country physician when he made his epochal discoveries, the French chemist and biologist Louis Pasteur disliked physicians so much that he would not have them as workers in his laboratory. Despite his disdain for physicians, he was deeply fascinated by diseases of various kinds. Pasteur discovered that putrefaction (a decomposition of organic substances) is caused by microorganisms that float in the air. Pasteur learned that he could prevent putrefaction by subjecting organic substances to moderate but not extreme heat, a process known as pasteurization.
In 1865 Joseph Lister, an English surgeon, read of Pasteur's research on putrefaction. Lister recalled that whereas simple bone fractures invariably healed, compound fractures (bone fractures bursting the skin) almost always began to putrefy. Lister was certain that this dangerous, infectious process was caused by the wretched microorganisms that Pasteur had described. To test his theory, Lister covered his patients' compound fractures, previously exposed to the air, with linen strips soaked in carbolic acid. He believed the carbolic acid might exterminate the airborne microorganisms.
Lister treated compound fractures and open surgical wounds with carbolic acid for nine months. During this time, he did not observe a single infection in his surgical ward. The results of his experiments, published in 1867, gave rise to antiseptic surgery. Although Lister's antiseptic technique initially encountered resistance from other physicians, it soon became widely accepted, and deaths due to infections in the operating room plummeted.
source: encarta enyclopedia
Vaccination
Smallpox, once a common viral infection that claimed millions of lives in periodic epidemics around the globe, is now considered fully eradicated. Much of the credit for this medical triumph belongs to the English physician Edward Jenner, who in 1796 developed the first effective vaccine against smallpox. Jenner's discovery laid the foundations for the science of immunology. Vaccines are now used to control and prevent diphtheria, hepatitis, influenza, meningitis, polio, tetanus, typhoid fever, whooping cough, and many other diseases that once plagued humankind.
In Jenner's day a procedure called variolation was used to protect people against smallpox. The procedure involved scratching a bit of the substance from smallpox blisters—obtained from a person with a mild case of the disease—into a healthy person's arm. Hopefully, a mild case of the disease would develop and pass, but the procedure was often deadly.
Jenner, orphaned at the age of five, was born and raised in the tiny English village of Berkeley, near Bristol. At the age of 13, Jenner was apprenticed to a country surgeon. Shortly after, milkmaids told him that after they contracted cowpox, a harmless disease confined usually to their hands and arms, they never got smallpox.
Following his training with the famous surgeon John Hunter in London, Jenner returned to Berkeley and devised an experiment to learn whether cowpox could protect against smallpox. On May 14, 1796, Jenner made two small scratches on the arm of an eight-year-old boy named James Phipps. On those scratches he rubbed fluid from a milkmaid's cowpox blister. Eight days later, Phipps developed small cowpox blisters on the scratches. On July 1 Jenner variolated Phipps with fluid from a smallpox blister. Phipps never got even a mild case of smallpox.
Jenner had made two important discoveries: Cowpox protects against smallpox, and cowpox could be transmitted from person to person. He subsequently vaccinated another eight children, including his own son, experimenting further with his new technique. In 1798 Jenner submitted his findings to Philosophical Transactions, but his work was rejected. After further experiments, he published his results himself, paying for the printing.
Vaccination was initially viewed as unnatural, and the technique encountered significant opposition for decades. More than 80 years passed before Pasteur, drawing on Jenner's work, opened the way for the development of modern preventive vaccines. In the end, however, Jenner received an honorary degree from Oxford University for his groundbreaking work.
source: encarta encyclopedia
Smallpox, once a common viral infection that claimed millions of lives in periodic epidemics around the globe, is now considered fully eradicated. Much of the credit for this medical triumph belongs to the English physician Edward Jenner, who in 1796 developed the first effective vaccine against smallpox. Jenner's discovery laid the foundations for the science of immunology. Vaccines are now used to control and prevent diphtheria, hepatitis, influenza, meningitis, polio, tetanus, typhoid fever, whooping cough, and many other diseases that once plagued humankind.
In Jenner's day a procedure called variolation was used to protect people against smallpox. The procedure involved scratching a bit of the substance from smallpox blisters—obtained from a person with a mild case of the disease—into a healthy person's arm. Hopefully, a mild case of the disease would develop and pass, but the procedure was often deadly.
Jenner, orphaned at the age of five, was born and raised in the tiny English village of Berkeley, near Bristol. At the age of 13, Jenner was apprenticed to a country surgeon. Shortly after, milkmaids told him that after they contracted cowpox, a harmless disease confined usually to their hands and arms, they never got smallpox.
Following his training with the famous surgeon John Hunter in London, Jenner returned to Berkeley and devised an experiment to learn whether cowpox could protect against smallpox. On May 14, 1796, Jenner made two small scratches on the arm of an eight-year-old boy named James Phipps. On those scratches he rubbed fluid from a milkmaid's cowpox blister. Eight days later, Phipps developed small cowpox blisters on the scratches. On July 1 Jenner variolated Phipps with fluid from a smallpox blister. Phipps never got even a mild case of smallpox.
Jenner had made two important discoveries: Cowpox protects against smallpox, and cowpox could be transmitted from person to person. He subsequently vaccinated another eight children, including his own son, experimenting further with his new technique. In 1798 Jenner submitted his findings to Philosophical Transactions, but his work was rejected. After further experiments, he published his results himself, paying for the printing.
Vaccination was initially viewed as unnatural, and the technique encountered significant opposition for decades. More than 80 years passed before Pasteur, drawing on Jenner's work, opened the way for the development of modern preventive vaccines. In the end, however, Jenner received an honorary degree from Oxford University for his groundbreaking work.
source: encarta encyclopedia
Surgical Anesthesia
Until the discovery of anesthesia by Crawford Williamson Long in 1842, surgery was an excruciating ordeal, usually attempted only in cases of dire injury or illness. Some patients used alcohol or opium to lessen the pain; others recited verse. Passing out was a blessing. Surgeons worked at breakneck speed to get in and out of the patient's body as quickly as possible. Anesthesia changed all this, permitting surgeons to work at a slower, more careful pace.
The Spaniard Lullius discovered ether, an organic solvent, in 1275, but its anesthetic properties were unknown. In the early 1800s people inhaled ether at parties to make themselves high. Long, a physician in Jefferson, Georgia, frequently prepared ether at the request of his friends. One evening he used it himself at a so-called ether frolic and badly bruised himself while he was high. Yet, Long noticed, he felt no pain.
On March 30, 1842, Long convinced James Venable, who had two cysts in his neck and was terrified at the prospect of surgery, to try ether. Venable did, and the ether made him unconscious. The operation was a success, and Venable, amazed, felt no pain at all. During the next four years, Long successfully used ether as anesthesia on eight patients.
But in 1842 the physician Charles Jackson and a dentist, William Morton, learned what Long was doing with ether and stole his secret, possibly after visiting Jefferson. Morton used ether to anesthetize two patients at Boston's Massachusetts General Hospital on October 16, 1846, in front of an audience of famous surgeons. The results were published, and anesthesia was soon used around the world. Long received no credit for the discovery.
The claims of Jackson, Morton, Long, and others created bitter quarrels about who actually invented surgical anesthesia. The Congress of the United States even took up the matter, debating the issue for 16 years without ever deciding who first introduced ether as an anesthetic procedure. But the use of anesthesia developed rapidly. Later, scientists found new anesthetic agents, developed better methods of administering anesthetic gases, and eventually discovered the use of local anesthesia.
source: encarta encyclopedia
Until the discovery of anesthesia by Crawford Williamson Long in 1842, surgery was an excruciating ordeal, usually attempted only in cases of dire injury or illness. Some patients used alcohol or opium to lessen the pain; others recited verse. Passing out was a blessing. Surgeons worked at breakneck speed to get in and out of the patient's body as quickly as possible. Anesthesia changed all this, permitting surgeons to work at a slower, more careful pace.
The Spaniard Lullius discovered ether, an organic solvent, in 1275, but its anesthetic properties were unknown. In the early 1800s people inhaled ether at parties to make themselves high. Long, a physician in Jefferson, Georgia, frequently prepared ether at the request of his friends. One evening he used it himself at a so-called ether frolic and badly bruised himself while he was high. Yet, Long noticed, he felt no pain.
On March 30, 1842, Long convinced James Venable, who had two cysts in his neck and was terrified at the prospect of surgery, to try ether. Venable did, and the ether made him unconscious. The operation was a success, and Venable, amazed, felt no pain at all. During the next four years, Long successfully used ether as anesthesia on eight patients.
But in 1842 the physician Charles Jackson and a dentist, William Morton, learned what Long was doing with ether and stole his secret, possibly after visiting Jefferson. Morton used ether to anesthetize two patients at Boston's Massachusetts General Hospital on October 16, 1846, in front of an audience of famous surgeons. The results were published, and anesthesia was soon used around the world. Long received no credit for the discovery.
The claims of Jackson, Morton, Long, and others created bitter quarrels about who actually invented surgical anesthesia. The Congress of the United States even took up the matter, debating the issue for 16 years without ever deciding who first introduced ether as an anesthetic procedure. But the use of anesthesia developed rapidly. Later, scientists found new anesthetic agents, developed better methods of administering anesthetic gases, and eventually discovered the use of local anesthesia.
source: encarta encyclopedia
X rays
The development of X-ray photography, or radiology, was an enormous leap into the future: For the first time, physicians could see inside the body without opening it. With X rays surgeons could quickly diagnose fractures, tumors, and other ailments and plan more intricate operations. As a result, surgery rapidly grew in sophistication.
Early in 1895 German physicist Wilhelm Conrad Roentgen was experimenting with a Crookes tube—a pear-shaped glass tube emptied of air with electrodes (metal wires) sealed into opposite ends of the tube. When the negative electrode, or cathode, received a high-voltage electric current, it glowed white-hot and emitted a stream of invisible, electrically charged particles called cathode rays. These rays moved towards the positive electrode, or anode, of the tube. If only a little air remained inside the Crookes tube, the cathode rays striking the glass at the other end of the tube would produce a yellow-green fluorescence.
Roentgen's experiments had confirmed another physicist's observation that cathode rays could pass through an aluminum-covered window in the wall of a Crookes tube. To discover whether cathode rays could also go through the glass wall of a Crookes tube, he placed a piece of paper coated with a barium salt near the tube's anode. Such paper was known to fluoresce when hit with cathode rays. He expected the fluorescence to be faint, so he covered the tube with black cardboard to block the tube's fluorescence and to better help him see. He also darkened his laboratory.
While testing the tube to see whether any fluorescence was visible through the cardboard, Roentgen noticed a strange glow some distance away. Lighting a match for light to see, he discovered that the glow was coming from another piece of coated paper that was about a meter away from the Crookes tube. Repeatedly turning his tube on and off, he learned that the paper only glowed when the tube was on. The paper still fluoresced when he moved it even farther away and even when he shielded it, first with a pack of cards and then with a book.
Roentgen knew that cathode rays were not strong enough to cause this distant fluorescence. There could only be one explanation: The Crookes tube was producing previously unknown kinds of electromagnetic waves, which he later called X rays. Further experiments showed that these new X rays would not go through lead and would go only partly through other metals.
In December 1895 he X-rayed his own fingers holding a small lead pipe. To his astonishment, the developed pictures revealed not only the shadow of the pipe but also the bones of two of his fingers. He later X-rayed the left hand of his wife, Bertha, who had two gold rings on her fourth finger, and showed the terrified woman a picture of her own bones, complete with rings.
Roentgen's preliminary report, entitled On a New Kind of X Ray, was published only a few days after he submitted it, a record for rapid publication in science. In 1901 Roentgen became the first scientist ever to receive the Nobel Prize in physics.
X rays were used immediately for medical diagnosis but did not become a routine procedure until the 1920s. In the decades that followed, technological advances allowed X rays to outline individual organs and organ systems, as well as arteries and veins. In 1972 researchers developed the computerized tomography (CAT) scan, a sophisticated X-ray technology that produces computer-generated cross-sectional views of the body.
source: encarta encyclopedia
The development of X-ray photography, or radiology, was an enormous leap into the future: For the first time, physicians could see inside the body without opening it. With X rays surgeons could quickly diagnose fractures, tumors, and other ailments and plan more intricate operations. As a result, surgery rapidly grew in sophistication.
Early in 1895 German physicist Wilhelm Conrad Roentgen was experimenting with a Crookes tube—a pear-shaped glass tube emptied of air with electrodes (metal wires) sealed into opposite ends of the tube. When the negative electrode, or cathode, received a high-voltage electric current, it glowed white-hot and emitted a stream of invisible, electrically charged particles called cathode rays. These rays moved towards the positive electrode, or anode, of the tube. If only a little air remained inside the Crookes tube, the cathode rays striking the glass at the other end of the tube would produce a yellow-green fluorescence.
Roentgen's experiments had confirmed another physicist's observation that cathode rays could pass through an aluminum-covered window in the wall of a Crookes tube. To discover whether cathode rays could also go through the glass wall of a Crookes tube, he placed a piece of paper coated with a barium salt near the tube's anode. Such paper was known to fluoresce when hit with cathode rays. He expected the fluorescence to be faint, so he covered the tube with black cardboard to block the tube's fluorescence and to better help him see. He also darkened his laboratory.
While testing the tube to see whether any fluorescence was visible through the cardboard, Roentgen noticed a strange glow some distance away. Lighting a match for light to see, he discovered that the glow was coming from another piece of coated paper that was about a meter away from the Crookes tube. Repeatedly turning his tube on and off, he learned that the paper only glowed when the tube was on. The paper still fluoresced when he moved it even farther away and even when he shielded it, first with a pack of cards and then with a book.
Roentgen knew that cathode rays were not strong enough to cause this distant fluorescence. There could only be one explanation: The Crookes tube was producing previously unknown kinds of electromagnetic waves, which he later called X rays. Further experiments showed that these new X rays would not go through lead and would go only partly through other metals.
In December 1895 he X-rayed his own fingers holding a small lead pipe. To his astonishment, the developed pictures revealed not only the shadow of the pipe but also the bones of two of his fingers. He later X-rayed the left hand of his wife, Bertha, who had two gold rings on her fourth finger, and showed the terrified woman a picture of her own bones, complete with rings.
Roentgen's preliminary report, entitled On a New Kind of X Ray, was published only a few days after he submitted it, a record for rapid publication in science. In 1901 Roentgen became the first scientist ever to receive the Nobel Prize in physics.
X rays were used immediately for medical diagnosis but did not become a routine procedure until the 1920s. In the decades that followed, technological advances allowed X rays to outline individual organs and organ systems, as well as arteries and veins. In 1972 researchers developed the computerized tomography (CAT) scan, a sophisticated X-ray technology that produces computer-generated cross-sectional views of the body.
source: encarta encyclopedia
Blood Typing
At the dawn of the 20th century, the Austrian physician Karl Landsteiner made the extraordinary discovery that human blood could be grouped into several different types. This discovery made possible the transfer of blood from one human to another—a medical breakthrough that has saved countless lives.
Prior to Landsteiner's pioneering work, there were few reports on the transfer of blood from one human to another. In 1668 Jean Baptiste Denis, the French physician to King Louis XIV, dared to transfuse a man with sheep's blood. The man eventually died and Denis was arrested for murder. Transfusions were quickly banned in France and England. Other attempted transfusions using human blood were frequently unsuccessful, and patients often died due to blood incompatibility.
In 1900 Landsteiner made the brilliant observation that human blood contains what he called isoagglutinins. These proteins are capable of agglutinating, or clotting, the red blood cells of blood samples containing isoagglutinins different from their own. He thus was able to divide blood into three types: A, B, and O. A rare fourth type, AB, was later discovered.
Landsteiner showed that the sera of two blood samples containing the same isoagglutinins would not clot the red cells of either blood. This discovery permitted the development of a system for safe blood transfusions. For this gift to humankind, Landsteiner received the Nobel Prize in physiology or medicine in 1930.
source: encarta encyclopedia
At the dawn of the 20th century, the Austrian physician Karl Landsteiner made the extraordinary discovery that human blood could be grouped into several different types. This discovery made possible the transfer of blood from one human to another—a medical breakthrough that has saved countless lives.
Prior to Landsteiner's pioneering work, there were few reports on the transfer of blood from one human to another. In 1668 Jean Baptiste Denis, the French physician to King Louis XIV, dared to transfuse a man with sheep's blood. The man eventually died and Denis was arrested for murder. Transfusions were quickly banned in France and England. Other attempted transfusions using human blood were frequently unsuccessful, and patients often died due to blood incompatibility.
In 1900 Landsteiner made the brilliant observation that human blood contains what he called isoagglutinins. These proteins are capable of agglutinating, or clotting, the red blood cells of blood samples containing isoagglutinins different from their own. He thus was able to divide blood into three types: A, B, and O. A rare fourth type, AB, was later discovered.
Landsteiner showed that the sera of two blood samples containing the same isoagglutinins would not clot the red cells of either blood. This discovery permitted the development of a system for safe blood transfusions. For this gift to humankind, Landsteiner received the Nobel Prize in physiology or medicine in 1930.
source: encarta encyclopedia
Tissue Culture
In 1907 American biologist Ross Granville Harrison stumbled upon the amazing discovery that living tissues could be cultured, or grown, outside the body. Although Harrison could not have known it at the time, his discovery would become one of the most valued techniques in medicine. Tissue culture has opened up new ways to study the development of genes (the basic units of heredity), embryos, tumors, toxins, and the pathogens that cause numerous diseases. The technique is also used to produce medicines, vaccines, and replacement tissues, as well as to clone animals, such as Dolly, the famous sheep.
In late summer of 1906 Harrison, an expert on embryos, wanted to solve what was then an important problem in biology. Harrison set out to determine whether nerve fibers grow in local tissues of the body or originate in nerve cells of the brain. He had to devise a new way to study the problem because all the available living specimens contained both nerves and surrounding tissue.
Harrison decided to study living nerves in the absence of any surrounding tissue. To do this, he isolated a portion of the hindbrain of a tiny living frog embryo. To keep his specimen alive, he immersed it in fresh frog lymph (a diluted blood plasma carried by the lymphatic system) and placed it under a cover slip so he could examine it with a microscope. The frog lymph quickly clotted, like blood, and he sealed it with wax to prevent evaporation or contamination of the specimen.
Using a microscope, Harrison discovered that the nerve fiber did actually come from the brain, not the surrounding tissue. Harrison noticed something else: The frog's brain cells were still growing, even though they were no longer in the frog's body. Harrison found the answer to the question he was asking and, at the same time, invented what would become the science of tissue culture. Harrison reported his result in May 1907. Since then tissue culture has allowed researchers to learn more about the basic mechanisms of disease than had been learned in the previous 500 years.
source: encarta encyclopedia
In 1907 American biologist Ross Granville Harrison stumbled upon the amazing discovery that living tissues could be cultured, or grown, outside the body. Although Harrison could not have known it at the time, his discovery would become one of the most valued techniques in medicine. Tissue culture has opened up new ways to study the development of genes (the basic units of heredity), embryos, tumors, toxins, and the pathogens that cause numerous diseases. The technique is also used to produce medicines, vaccines, and replacement tissues, as well as to clone animals, such as Dolly, the famous sheep.
In late summer of 1906 Harrison, an expert on embryos, wanted to solve what was then an important problem in biology. Harrison set out to determine whether nerve fibers grow in local tissues of the body or originate in nerve cells of the brain. He had to devise a new way to study the problem because all the available living specimens contained both nerves and surrounding tissue.
Harrison decided to study living nerves in the absence of any surrounding tissue. To do this, he isolated a portion of the hindbrain of a tiny living frog embryo. To keep his specimen alive, he immersed it in fresh frog lymph (a diluted blood plasma carried by the lymphatic system) and placed it under a cover slip so he could examine it with a microscope. The frog lymph quickly clotted, like blood, and he sealed it with wax to prevent evaporation or contamination of the specimen.
Using a microscope, Harrison discovered that the nerve fiber did actually come from the brain, not the surrounding tissue. Harrison noticed something else: The frog's brain cells were still growing, even though they were no longer in the frog's body. Harrison found the answer to the question he was asking and, at the same time, invented what would become the science of tissue culture. Harrison reported his result in May 1907. Since then tissue culture has allowed researchers to learn more about the basic mechanisms of disease than had been learned in the previous 500 years.
source: encarta encyclopedia
Antibiotics
The discovery of antibiotics opened a whole new front in the war against disease. Armed with antibiotics, which act by killing bacteria or inhibiting their growth, scientists have mounted a major assault on cholera, pneumonia, tetanus, tuberculosis, and many other deadly bacterial infections that had previously struck people down relentlessly.
Some of the most important breakthroughs in science occur unexpectedly, and the discovery of penicillin—perhaps the world's most widely used antibiotic—is one such example. The British bacteriologist Sir Alexander Fleming is credited with discovering penicillin, although other scientists before him had noticed that the mold Penicillium notatum prevented the growth of some types of bacteria. So Fleming's discovery was actually a rediscovery.
In September 1928 Fleming was preparing to take a short vacation with his family, when a series of almost unbelievably lucky events occurred. Just before leaving, Fleming decided to cultivate staphylococci to study when he returned. This was the first piece of luck. He could have picked any bacterium to study, but he happened to pick one that would turn out to be susceptible to penicillin.
Fleming opened a petri dish for a few seconds to put the staphylococci inside. Ordinarily, no mold spores would have a chance to get in the dish, but two floors below his laboratory, another scientist was studying the mold Penicillium notatum. Millions of very light mold spores floated in the air, up the staircase and the elevator shaft, through the always-open doors of Fleming's laboratory, and into the open dish where, luckily, he was just putting the staphylococci.
Fleming, preoccupied with his vacation, left the petri dish on the laboratory bench instead of putting it in a warm incubator. This was lucky, too, because the bacteria and Penicillium notatum usually grow at different temperatures. Staphylococci multiply at relatively high temperatures, while Penicillium multiplies at lower temperatures. While Fleming was away the temperature turned out to be perfect for Penicillium, but not so good for the staphylococci, which grew slowly. The Penicillium mold thrived and secreted penicillin, which oozed around the dish, preventing the growth of staphylococci and leaving the Penicillium mold isolated from small bacterial colonies in the dish.
Fleming, upon his return, immediately realized what had happened, and he conducted other tests to learn what other bacteria this mysterious mold stuff could kill. He also tried to make pure penicillin, but did not succeed. Fleming believed that the mold substance, which he named penicillin, could be rubbed onto a cut or a scrape to prevent an infection. A few years later, however, Fleming gave up studying the mold.
As a consequence, penicillin was nearly forgotten until the beginning of World War II (1939-1945). Scientists at Oxford University in England showed that penicillin could prevent bacterial infections in animals and humans, and they devised a technique to mass-produce pure penicillin. The scientists encouraged companies in the United States to manufacture penicillin in vast quantities, and the new drug was credited with saving thousands of lives during the war. In 1945 Fleming and two of the Oxford scientists, Sir Howard Florey and Ernst B. Chain, received the Nobel Prize in physiology or medicine.
source: encarta encyclopedia
The discovery of antibiotics opened a whole new front in the war against disease. Armed with antibiotics, which act by killing bacteria or inhibiting their growth, scientists have mounted a major assault on cholera, pneumonia, tetanus, tuberculosis, and many other deadly bacterial infections that had previously struck people down relentlessly.
Some of the most important breakthroughs in science occur unexpectedly, and the discovery of penicillin—perhaps the world's most widely used antibiotic—is one such example. The British bacteriologist Sir Alexander Fleming is credited with discovering penicillin, although other scientists before him had noticed that the mold Penicillium notatum prevented the growth of some types of bacteria. So Fleming's discovery was actually a rediscovery.
In September 1928 Fleming was preparing to take a short vacation with his family, when a series of almost unbelievably lucky events occurred. Just before leaving, Fleming decided to cultivate staphylococci to study when he returned. This was the first piece of luck. He could have picked any bacterium to study, but he happened to pick one that would turn out to be susceptible to penicillin.
Fleming opened a petri dish for a few seconds to put the staphylococci inside. Ordinarily, no mold spores would have a chance to get in the dish, but two floors below his laboratory, another scientist was studying the mold Penicillium notatum. Millions of very light mold spores floated in the air, up the staircase and the elevator shaft, through the always-open doors of Fleming's laboratory, and into the open dish where, luckily, he was just putting the staphylococci.
Fleming, preoccupied with his vacation, left the petri dish on the laboratory bench instead of putting it in a warm incubator. This was lucky, too, because the bacteria and Penicillium notatum usually grow at different temperatures. Staphylococci multiply at relatively high temperatures, while Penicillium multiplies at lower temperatures. While Fleming was away the temperature turned out to be perfect for Penicillium, but not so good for the staphylococci, which grew slowly. The Penicillium mold thrived and secreted penicillin, which oozed around the dish, preventing the growth of staphylococci and leaving the Penicillium mold isolated from small bacterial colonies in the dish.
Fleming, upon his return, immediately realized what had happened, and he conducted other tests to learn what other bacteria this mysterious mold stuff could kill. He also tried to make pure penicillin, but did not succeed. Fleming believed that the mold substance, which he named penicillin, could be rubbed onto a cut or a scrape to prevent an infection. A few years later, however, Fleming gave up studying the mold.
As a consequence, penicillin was nearly forgotten until the beginning of World War II (1939-1945). Scientists at Oxford University in England showed that penicillin could prevent bacterial infections in animals and humans, and they devised a technique to mass-produce pure penicillin. The scientists encouraged companies in the United States to manufacture penicillin in vast quantities, and the new drug was credited with saving thousands of lives during the war. In 1945 Fleming and two of the Oxford scientists, Sir Howard Florey and Ernst B. Chain, received the Nobel Prize in physiology or medicine.
source: encarta encyclopedia
DNA
Perhaps the greatest medical breakthrough of the 20th century is the discovery of the structure of deoxyribonucleic acid (DNA—the molecular basis of heredity). Knowledge of DNA's chemical structure allowed scientists to understand for the first time how DNA replicates itself and passes information from one generation to the next. This monumental discovery has already revolutionized many aspects of medicine, permitting the development of a vast range of genetically engineered drugs, hormones, and other useful substances. Even more radical changes are afoot. In the new millennium, scientists are expected to have access to a complete map of the human genetic code, which should help them trace the genetic causes of all inherited diseases and search out possible cures.
The Swiss physician Friedrich Miescher isolated DNA for the first time in 1869, but the function of the chemical, which is found only in the nucleus of cells, was unknown. As the years passed, scientists learned that DNA contained phosphate, a sugar called deoxyribose, and four different compounds called nucleotide bases.
In 1944 the Canadian-born American physician and bacteriologist Oswald T. Avery and his colleagues showed, in a series of experiments on bacteria, that DNA transmitted genetic information. Prior to Avery's groundbreaking work, many biochemists believed that proteins were the source of genetic information.
By 1950 two groups of scientists were in hot pursuit of the structure of DNA. One of the groups was at Cavendish Laboratory in Cambridge, England. The other group, at King's College, London, consisted of Maurice Wilkins, a physicist, and Raymond Gosling, a graduate student. They were joined in 1951 by Rosalind Franklin, an expert in X-ray crystallography (a technique that uses a tiny beam of X rays to create images of the structural relationships between atoms and molecules of chemical substances). Photographs of images produced by X-ray crystallography are called X-ray diffraction photographs.
In 1950 Wilkins received a uniquely pure sample of DNA from a Swiss physicist. From this sample, he was able to pick out single DNA fibers with a glass rod. Wilkins and Gosling X-rayed these fibers in 1950, as did Franklin when she joined the laboratory in 1951.
However, a misunderstanding caused Wilkins and Franklin each to think they were in charge of X-ray crystallography, and they did not cooperate. When Franklin left the team in 1952, she was ordered to submit all of the X-ray diffraction photographs to Wilkins. One of these photographs showed that the DNA molecule had the shape of a double helix, a structure resembling a twisted ladder.
In the meantime the American biologist James Watson attended a meeting in Naples, Italy, in 1950, in which he saw one of Wilkins's X-ray diffraction photographs. Watson immediately thought the molecule might be a double helix. In the fall of 1951 he joined the team of scientists at Cavendish Laboratory, where he convinced a British biophysicist, Francis Crick, that a combination of model building—using plastic balls, wires and steel plates—and X-ray crystallography could lead them to the structure of DNA.
The double helix by itself, however, was not the only secret to the DNA molecule. Its entire chemistry needed to be explained. Watson, unbeknownst to Wilkins, was now convinced that DNA had a helical structure and was working feverishly with Crick on their increasingly complex model of the molecule, which they finished during the second week of 1953. This model incorporated all the known chemical components of DNA and closely matched the diffraction pattern observed in Wilkin's photograph. Watson and Crick accurately deduced that the two strands of the double helix separated before cellular division, providing templates, or patterns, for the creation of two new DNA molecules identical to the original.
Watson and Crick sent Wilkins a copy of their manuscript, which took advantage, of course, of what Wilkins and Franklin had done, and which Wilkins thought was his own. After reading their manuscript, Wilkins sent them a letter that began, “I think you are a couple of old rogues.…”
On April 25, 1953, the journal Nature published one article from the Cambridge laboratory and two from King's College in London on the molecular structure of DNA. Many felt that the key to life itself had been revealed. Wilkins, Watson, and Crick shared the 1962 Nobel Prize in physiology or medicine.
source: encarta encyclopedia
Perhaps the greatest medical breakthrough of the 20th century is the discovery of the structure of deoxyribonucleic acid (DNA—the molecular basis of heredity). Knowledge of DNA's chemical structure allowed scientists to understand for the first time how DNA replicates itself and passes information from one generation to the next. This monumental discovery has already revolutionized many aspects of medicine, permitting the development of a vast range of genetically engineered drugs, hormones, and other useful substances. Even more radical changes are afoot. In the new millennium, scientists are expected to have access to a complete map of the human genetic code, which should help them trace the genetic causes of all inherited diseases and search out possible cures.
The Swiss physician Friedrich Miescher isolated DNA for the first time in 1869, but the function of the chemical, which is found only in the nucleus of cells, was unknown. As the years passed, scientists learned that DNA contained phosphate, a sugar called deoxyribose, and four different compounds called nucleotide bases.
In 1944 the Canadian-born American physician and bacteriologist Oswald T. Avery and his colleagues showed, in a series of experiments on bacteria, that DNA transmitted genetic information. Prior to Avery's groundbreaking work, many biochemists believed that proteins were the source of genetic information.
By 1950 two groups of scientists were in hot pursuit of the structure of DNA. One of the groups was at Cavendish Laboratory in Cambridge, England. The other group, at King's College, London, consisted of Maurice Wilkins, a physicist, and Raymond Gosling, a graduate student. They were joined in 1951 by Rosalind Franklin, an expert in X-ray crystallography (a technique that uses a tiny beam of X rays to create images of the structural relationships between atoms and molecules of chemical substances). Photographs of images produced by X-ray crystallography are called X-ray diffraction photographs.
In 1950 Wilkins received a uniquely pure sample of DNA from a Swiss physicist. From this sample, he was able to pick out single DNA fibers with a glass rod. Wilkins and Gosling X-rayed these fibers in 1950, as did Franklin when she joined the laboratory in 1951.
However, a misunderstanding caused Wilkins and Franklin each to think they were in charge of X-ray crystallography, and they did not cooperate. When Franklin left the team in 1952, she was ordered to submit all of the X-ray diffraction photographs to Wilkins. One of these photographs showed that the DNA molecule had the shape of a double helix, a structure resembling a twisted ladder.
In the meantime the American biologist James Watson attended a meeting in Naples, Italy, in 1950, in which he saw one of Wilkins's X-ray diffraction photographs. Watson immediately thought the molecule might be a double helix. In the fall of 1951 he joined the team of scientists at Cavendish Laboratory, where he convinced a British biophysicist, Francis Crick, that a combination of model building—using plastic balls, wires and steel plates—and X-ray crystallography could lead them to the structure of DNA.
The double helix by itself, however, was not the only secret to the DNA molecule. Its entire chemistry needed to be explained. Watson, unbeknownst to Wilkins, was now convinced that DNA had a helical structure and was working feverishly with Crick on their increasingly complex model of the molecule, which they finished during the second week of 1953. This model incorporated all the known chemical components of DNA and closely matched the diffraction pattern observed in Wilkin's photograph. Watson and Crick accurately deduced that the two strands of the double helix separated before cellular division, providing templates, or patterns, for the creation of two new DNA molecules identical to the original.
Watson and Crick sent Wilkins a copy of their manuscript, which took advantage, of course, of what Wilkins and Franklin had done, and which Wilkins thought was his own. After reading their manuscript, Wilkins sent them a letter that began, “I think you are a couple of old rogues.…”
On April 25, 1953, the journal Nature published one article from the Cambridge laboratory and two from King's College in London on the molecular structure of DNA. Many felt that the key to life itself had been revealed. Wilkins, Watson, and Crick shared the 1962 Nobel Prize in physiology or medicine.
source: encarta encyclopedia
Looking Ahead
The discovery of the structure of DNA—like the discovery of X rays at the end of the 19th century or the detection of bacteria more than two centuries before that—has radically altered medicine and opened previously unknown frontiers. Equipped with a map of the human genome (the complete genetic code), researchers in the next millennium hope to root out the genetic causes of a wide range of inherited diseases, from schizophrenia to cystic fibrosis to hemophilia to many types of cancer. Of perhaps greater significance, many scientists believe that advances in molecular genetics are setting the course for fundamental changes in the diagnosis and treatment of disease. Instead of merely treating the symptoms of disease, as they do now, physicians of the next millennium may develop the ability to routinely identify and correct the causes of disease before symptoms appear.
And yet, despite Western medicine's stunning success in fighting disease and extending human life, the health of much of the developing world is worsening. Modern vaccines and antibiotics would save tens of millions of lives each year throughout the developing world, where people are continuously struck down by malaria, tuberculosis, polio, pneumonia, and other easily treatable disorders. And the vast majority of people with acquired immune deficiency syndrome (AIDS) now live in the developing world, where access to costly life-extending medications is beyond the reach of most of those infected. Finding ways to extend the magnificent contributions of Western medicine to those who need it most therefore constitutes one of the greatest medical challenges of the coming millennium.
source: encarta encyclopedia
The discovery of the structure of DNA—like the discovery of X rays at the end of the 19th century or the detection of bacteria more than two centuries before that—has radically altered medicine and opened previously unknown frontiers. Equipped with a map of the human genome (the complete genetic code), researchers in the next millennium hope to root out the genetic causes of a wide range of inherited diseases, from schizophrenia to cystic fibrosis to hemophilia to many types of cancer. Of perhaps greater significance, many scientists believe that advances in molecular genetics are setting the course for fundamental changes in the diagnosis and treatment of disease. Instead of merely treating the symptoms of disease, as they do now, physicians of the next millennium may develop the ability to routinely identify and correct the causes of disease before symptoms appear.
And yet, despite Western medicine's stunning success in fighting disease and extending human life, the health of much of the developing world is worsening. Modern vaccines and antibiotics would save tens of millions of lives each year throughout the developing world, where people are continuously struck down by malaria, tuberculosis, polio, pneumonia, and other easily treatable disorders. And the vast majority of people with acquired immune deficiency syndrome (AIDS) now live in the developing world, where access to costly life-extending medications is beyond the reach of most of those infected. Finding ways to extend the magnificent contributions of Western medicine to those who need it most therefore constitutes one of the greatest medical challenges of the coming millennium.
source: encarta encyclopedia
The Authors
Meyer Friedman is a founder of the San Francisco-based Meyer Friedman Institute, a nonprofit research group. Gerald W. Friedland is a professor emeritus of radiology at Stanford University. Friedman and Friedland are coauthors of Medicine's 10 Greatest Discoveries, recently published by Yale University Press.
For further reading:
Fisher, Richard B. Edward Jenner, 1749-1823. Andre Deutsch, 1991.
Fradin, Dennis Brindell. “We Have Conquered Pain:” The Discovery of Anesthesia. Margaret McElderry, 1996.
Friedman, Meyer, and Gerald W. Friedland. Medicine's 10 Greatest Discoveries. Yale University Press, 1998.
Judson, Horace Freeland. The Eighth Day of Creation: Makers of the Revolution in Biology. Simon and Schuster, 1996.
Kevles, Bettyann Holtzmann. Naked to the Bone: Medical Imaging in the Twentieth Century. Rutgers University Press, 1996.
O'Malley, C. D. Andreas Vesalius of Brussels, 1514-1564. University of California Press, 1964.
Porter, Roy. The Cambridge Illustrated History of Medicine. Cambridge University Press, 1996.
source: encarta encyclopedia
For further reading:
Fisher, Richard B. Edward Jenner, 1749-1823. Andre Deutsch, 1991.
Fradin, Dennis Brindell. “We Have Conquered Pain:” The Discovery of Anesthesia. Margaret McElderry, 1996.
Friedman, Meyer, and Gerald W. Friedland. Medicine's 10 Greatest Discoveries. Yale University Press, 1998.
Judson, Horace Freeland. The Eighth Day of Creation: Makers of the Revolution in Biology. Simon and Schuster, 1996.
Kevles, Bettyann Holtzmann. Naked to the Bone: Medical Imaging in the Twentieth Century. Rutgers University Press, 1996.
O'Malley, C. D. Andreas Vesalius of Brussels, 1514-1564. University of California Press, 1964.
Porter, Roy. The Cambridge Illustrated History of Medicine. Cambridge University Press, 1996.
source: encarta encyclopedia
Looking ahead on INSIGHT
From the Notebooks of
Leonardo da Vinci
The life and structure of things
Although the painter's eye sees but the surface of things it must in rendering the surface discern and interpret the organic structure that lies beneath. The representation of the human figure entails a knowledge of its anatomy and its proportions. Landscapes entail a study of the morphology of plants, of the formation of the earth, of the movements of water and wind.
This work must begin with the conception of man, and describe the nature of the womb and how the foetus lives in it, up to what stage it resides there and in what ways it quickens into life and feeds. Also its growth and what interval there is between one stage of growth and another. What it is that forces it out from the body of the mother, and for what reasons it sometimes comes out of the mother's womb before due time.
Then I will describe which are the members which after the boy is born, grow more than the others, and determine the proportions of a boy of one year. Then describe the fully grown man and woman, with their proportions, and the nature of their complexions, colour, and physiognomy.
Then how they are composed of veins, tendons, muscles, and bones. Then in four drawings represent four universal conditions of men. That is, mirth with various acts of laughter; and describe the cause of laughter. Weeping in various aspects with its causes. Strife with various acts of killing: flight, fear, ferocity, boldness, murder, and everything pertaining to such conditions. Then represent Labour with pulling, thrusting, carrying, stopping, supporting, and such-like things.
Further, I would describe attitudes and movements. Then perspective concerning the function of the eye; and of hearing—here I will speak of music—and treat of the other senses—and describe the nature of the five senses. This mechanism of man we will demonstrate with [drawings of] figures.
source: encarta encyclopedia
Leonardo da Vinci
The life and structure of things
Although the painter's eye sees but the surface of things it must in rendering the surface discern and interpret the organic structure that lies beneath. The representation of the human figure entails a knowledge of its anatomy and its proportions. Landscapes entail a study of the morphology of plants, of the formation of the earth, of the movements of water and wind.
This work must begin with the conception of man, and describe the nature of the womb and how the foetus lives in it, up to what stage it resides there and in what ways it quickens into life and feeds. Also its growth and what interval there is between one stage of growth and another. What it is that forces it out from the body of the mother, and for what reasons it sometimes comes out of the mother's womb before due time.
Then I will describe which are the members which after the boy is born, grow more than the others, and determine the proportions of a boy of one year. Then describe the fully grown man and woman, with their proportions, and the nature of their complexions, colour, and physiognomy.
Then how they are composed of veins, tendons, muscles, and bones. Then in four drawings represent four universal conditions of men. That is, mirth with various acts of laughter; and describe the cause of laughter. Weeping in various aspects with its causes. Strife with various acts of killing: flight, fear, ferocity, boldness, murder, and everything pertaining to such conditions. Then represent Labour with pulling, thrusting, carrying, stopping, supporting, and such-like things.
Further, I would describe attitudes and movements. Then perspective concerning the function of the eye; and of hearing—here I will speak of music—and treat of the other senses—and describe the nature of the five senses. This mechanism of man we will demonstrate with [drawings of] figures.
source: encarta encyclopedia
(a) Proportion
The theory of proportions had a great fascination for Renaissance artists. Their canons were not only intended as a means of artistic workmanship, they were meant to achieve harmony. Proportions in painting, sculpture, and architecture were like harmony in music and gave intense delight.
Proportion is not only found in numbers and measurements but also in sounds, weights, time, and position, and whatever power there may be.
The Roman architect Vitruvius had transmitted some data of a Greek canon for the proportions of the human figure and these were revived in Renaissance time. A drawing by Leonardo, now in the Academy at Venice, was reproduced in an edition of Vitruvius' book, published in 1511, in order to illustrate the statement that a well-made human body with arms outstretched and feet together can be inscribed in a square; while the same body spread-eagled occupies a circle described around the navel. The proportions of the human body are here related to the most perfect geometric figures and may be said to be integrated into the spherical cosmos. Leonardo endeavoured to verify and elaborate Vitruvius' mathematical formulae in order to put them on a scientific basis by empirical observations, and for this purpose he collected data from living models.
Geometry is infinite because every continuous quantity is divisible to infinity in one direction or the other. But the discontinuous quantity commences in unity and increases to infinity, and as it has been said the continuous quantity increases to infinity and decreases to infinity. And if you give me a line of twenty braccia I will tell you how to make one of twenty-one.
Every part of the whole must be in proportion to the whole … I would have the same thing understood as applying to all animals and plants.
From painting which serves the eye, the noblest sense, arises harmony of proportions; just as many different voices joined together and singing simultaneously produce a harmonious proportion which gives such satisfaction to the sense of hearing that listeners remain spellbound with admiration as if half alive. But the effect of the beautiful proportion of an angelic face in painting is much greater, for these proportions produce a harmonious concord which reaches the eye simultaneously, just as a chord in music affects the ear; and if this beautiful harmony be shown to the lover of her whose beauty is portrayed, he will without doubt remain spellbound in admiration and in a joy without parallel and superior to all other sensations.
The painter in his harmonious proportions makes the component parts react simultaneously so that they can be seen at one and the same time both together and separately; together, by viewing the design of the composition as a whole; and separately by viewing the design of its component parts.
Vitruvius, the architect, says in his work on architecture that the measurements of the human body are distributed by nature as follows: 4 fingers make 1 palm; 4 palms make 1 foot; 6 palms make 1 cubit; 4 cubits make a man's height; and 4 cubits make one pace; and 24 palms make a man; and these measures he used in buildings.
If you open your legs so much as to decrease your height by 1/14 and spread and raise your arms so that your middle fingers are on a level with the top of your head, you must know that the navel will be the centre of a circle of which the outspread limbs touch the circumference; and the space between the legs will form an equilateral triangle.
The span of a man's outspread arms is equal to his height.
From the roots of the hair to the bottom of the chin is the tenth part of a man's height; from the bottom of the chin to the crown of the head is the eighth of the man's height; from the top of the breast to the crown of the head is the sixth of the man; from the top of the breast to the roots of the hair is the seventh part of the whole height; from the nipples to the crown of the head is a fourth part of the man. The maximum width of the shoulders is the fourth part of the height; from the elbow to the tip of the middle finger is the fifth part; from the elbow to the end of the shoulder is the eighth part. The complete hand is the tenth part. The penis begins at the centre of the man. The foot is the seventh part of the man. From the sole of the foot to just below the knee is the fourth part of the man. From below the knee to where the penis begins is the fourth part of the man.
The distance between the chin and the nose and that between the eyebrows and the beginning of the hair is equal to the height of the ear and is a third of the face.
The length of the foot from the end of the toes to the heel goes twice into that from the heel to the knee, that is, where the leg-bone joins the thigh bone. The hand to the wrist goes four times into the distance from the tip of the longest finger to the shoulder-joint.
A man's width across the hips is equal to the distance from the top of the hip to the bottom of the buttock, when he stands equally balanced on both feet; and there is the same distance from the top of the hip to the armpit. The waist, or narrower part above the hips, will be half-way between the armpits and the bottom of the buttock.
Every man at three years is half the full height he will grow to at last.
There is a great difference in the length between the joints in men and boys. In man the distance from the shoulder joint to the elbow, and from the elbow to the tip of the thumb, and from one shoulder to the other, is in each instance two heads, while in a boy it is only one head; because Nature forms for us the size which is the home of the intellect before forming what contains the vital elements.
Remember to be very careful in giving your figures limbs that they should appear to be in proportion to the size of the body and agree with the age. Thus a youth has limbs that are not very muscular nor strongly veined, and the surface is delicate and round and tender in colour. In man the limbs are sinewy and muscular; while in old men the surface is wrinkled, rugged and knotty, and the veins very prominent.
Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
The theory of proportions had a great fascination for Renaissance artists. Their canons were not only intended as a means of artistic workmanship, they were meant to achieve harmony. Proportions in painting, sculpture, and architecture were like harmony in music and gave intense delight.
Proportion is not only found in numbers and measurements but also in sounds, weights, time, and position, and whatever power there may be.
The Roman architect Vitruvius had transmitted some data of a Greek canon for the proportions of the human figure and these were revived in Renaissance time. A drawing by Leonardo, now in the Academy at Venice, was reproduced in an edition of Vitruvius' book, published in 1511, in order to illustrate the statement that a well-made human body with arms outstretched and feet together can be inscribed in a square; while the same body spread-eagled occupies a circle described around the navel. The proportions of the human body are here related to the most perfect geometric figures and may be said to be integrated into the spherical cosmos. Leonardo endeavoured to verify and elaborate Vitruvius' mathematical formulae in order to put them on a scientific basis by empirical observations, and for this purpose he collected data from living models.
Geometry is infinite because every continuous quantity is divisible to infinity in one direction or the other. But the discontinuous quantity commences in unity and increases to infinity, and as it has been said the continuous quantity increases to infinity and decreases to infinity. And if you give me a line of twenty braccia I will tell you how to make one of twenty-one.
Every part of the whole must be in proportion to the whole … I would have the same thing understood as applying to all animals and plants.
From painting which serves the eye, the noblest sense, arises harmony of proportions; just as many different voices joined together and singing simultaneously produce a harmonious proportion which gives such satisfaction to the sense of hearing that listeners remain spellbound with admiration as if half alive. But the effect of the beautiful proportion of an angelic face in painting is much greater, for these proportions produce a harmonious concord which reaches the eye simultaneously, just as a chord in music affects the ear; and if this beautiful harmony be shown to the lover of her whose beauty is portrayed, he will without doubt remain spellbound in admiration and in a joy without parallel and superior to all other sensations.
The painter in his harmonious proportions makes the component parts react simultaneously so that they can be seen at one and the same time both together and separately; together, by viewing the design of the composition as a whole; and separately by viewing the design of its component parts.
Vitruvius, the architect, says in his work on architecture that the measurements of the human body are distributed by nature as follows: 4 fingers make 1 palm; 4 palms make 1 foot; 6 palms make 1 cubit; 4 cubits make a man's height; and 4 cubits make one pace; and 24 palms make a man; and these measures he used in buildings.
If you open your legs so much as to decrease your height by 1/14 and spread and raise your arms so that your middle fingers are on a level with the top of your head, you must know that the navel will be the centre of a circle of which the outspread limbs touch the circumference; and the space between the legs will form an equilateral triangle.
The span of a man's outspread arms is equal to his height.
From the roots of the hair to the bottom of the chin is the tenth part of a man's height; from the bottom of the chin to the crown of the head is the eighth of the man's height; from the top of the breast to the crown of the head is the sixth of the man; from the top of the breast to the roots of the hair is the seventh part of the whole height; from the nipples to the crown of the head is a fourth part of the man. The maximum width of the shoulders is the fourth part of the height; from the elbow to the tip of the middle finger is the fifth part; from the elbow to the end of the shoulder is the eighth part. The complete hand is the tenth part. The penis begins at the centre of the man. The foot is the seventh part of the man. From the sole of the foot to just below the knee is the fourth part of the man. From below the knee to where the penis begins is the fourth part of the man.
The distance between the chin and the nose and that between the eyebrows and the beginning of the hair is equal to the height of the ear and is a third of the face.
The length of the foot from the end of the toes to the heel goes twice into that from the heel to the knee, that is, where the leg-bone joins the thigh bone. The hand to the wrist goes four times into the distance from the tip of the longest finger to the shoulder-joint.
A man's width across the hips is equal to the distance from the top of the hip to the bottom of the buttock, when he stands equally balanced on both feet; and there is the same distance from the top of the hip to the armpit. The waist, or narrower part above the hips, will be half-way between the armpits and the bottom of the buttock.
Every man at three years is half the full height he will grow to at last.
There is a great difference in the length between the joints in men and boys. In man the distance from the shoulder joint to the elbow, and from the elbow to the tip of the thumb, and from one shoulder to the other, is in each instance two heads, while in a boy it is only one head; because Nature forms for us the size which is the home of the intellect before forming what contains the vital elements.
Remember to be very careful in giving your figures limbs that they should appear to be in proportion to the size of the body and agree with the age. Thus a youth has limbs that are not very muscular nor strongly veined, and the surface is delicate and round and tender in colour. In man the limbs are sinewy and muscular; while in old men the surface is wrinkled, rugged and knotty, and the veins very prominent.
Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.
(b) The Anatomy and Movement of the Body
The human body is a complex unity within the larger field of nature, a microcosm wherein the Elements and Powers of the universe were incorporated. In order to study its structure Leonardo dissected corpses and examined bones, joints, and muscles separately and in relation to one another, making drawings from many points of view and taking recourse to visual demonstration since an adequate description could not be given in words. According to him such visual demonstrations gave 'complete and accurate conceptions of the various shapes such as neither ancient nor modern writers have ever been able to give without an infinitely tedious and confused prolixity of writing and of time.' Moreover, there are not only the various points of view, the infinity of aspects to be considered, there are also the continuous successions of phases in movements. The circular movements of shoulder, arm, and hand, for instance, is suggestive of a pictorial continuity such as we may see on a strip of film.
The study of structure included that of function, of the manner in which actions and gestures were performed, how the various muscles work together in bending and straightening the joints; how the weight of a body is supported and balanced. Leonardo looked upon anatomy with the eye of a mechanician. Each limb, each organ was believed to be designed and perfectly adapted to perform its special function. Thus the muscles of the tongue were made to produce innumerable sounds within the mouth enabling man to pronounce many languages. In his time divisions between the various branches of anatomy did not exist. He investigated problems of physiology and embryology, the systems of nerves and arteries. He anticipated the principle of blood circulation and prepared the ground for further analyses on many subjects.
You who say that it is better to watch an anatomical demonstration than to see these drawings, you would be right if it were possible to observe all the details shown in such drawings in a single figure, in which with all your cleverness you will not see or acquire knowledge of more than some few veins, while in order to obtain a true and complete knowledge of these, I have dissected more than ten human bodies, destroying all the various members and removing the minutest particles of the flesh which surrounded these veins, without causing any effusion of blood other than the imperceptible bleeding of the capillary veins. And as one single body did not suffice for so long a time, it was necessary to proceed by stages with so many bodies as would render my knowledge complete; this I repeated twice in order to discover the differences. And though you should have a love for such things you may perhaps be deterred by natural repugnance, and if this does not prevent you, you may perhaps be deterred by fear of passing the night hours in the company of these corpses, quartered and flayed and horrible to behold; and if this does not deter you, then perhaps you may lack the skill in drawing, essential for such representation; and if you had the skill in drawing, it may not be combined with a knowledge of perspective; and if it is so combined you may not understand the methods of geometrical demonstration and the method of estimating the forces and strength of muscles; or perhaps you may be wanting in patience so that you will not be diligent.
Concerning which things, whether or no they have all been found in me, the hundred and twenty books which I have composed will give verdict 'yes' or 'no.' In these I have not been hindered either by avarice or negligence, but only by want of time. Farewell.
source: encarta encyclopedia
The human body is a complex unity within the larger field of nature, a microcosm wherein the Elements and Powers of the universe were incorporated. In order to study its structure Leonardo dissected corpses and examined bones, joints, and muscles separately and in relation to one another, making drawings from many points of view and taking recourse to visual demonstration since an adequate description could not be given in words. According to him such visual demonstrations gave 'complete and accurate conceptions of the various shapes such as neither ancient nor modern writers have ever been able to give without an infinitely tedious and confused prolixity of writing and of time.' Moreover, there are not only the various points of view, the infinity of aspects to be considered, there are also the continuous successions of phases in movements. The circular movements of shoulder, arm, and hand, for instance, is suggestive of a pictorial continuity such as we may see on a strip of film.
The study of structure included that of function, of the manner in which actions and gestures were performed, how the various muscles work together in bending and straightening the joints; how the weight of a body is supported and balanced. Leonardo looked upon anatomy with the eye of a mechanician. Each limb, each organ was believed to be designed and perfectly adapted to perform its special function. Thus the muscles of the tongue were made to produce innumerable sounds within the mouth enabling man to pronounce many languages. In his time divisions between the various branches of anatomy did not exist. He investigated problems of physiology and embryology, the systems of nerves and arteries. He anticipated the principle of blood circulation and prepared the ground for further analyses on many subjects.
You who say that it is better to watch an anatomical demonstration than to see these drawings, you would be right if it were possible to observe all the details shown in such drawings in a single figure, in which with all your cleverness you will not see or acquire knowledge of more than some few veins, while in order to obtain a true and complete knowledge of these, I have dissected more than ten human bodies, destroying all the various members and removing the minutest particles of the flesh which surrounded these veins, without causing any effusion of blood other than the imperceptible bleeding of the capillary veins. And as one single body did not suffice for so long a time, it was necessary to proceed by stages with so many bodies as would render my knowledge complete; this I repeated twice in order to discover the differences. And though you should have a love for such things you may perhaps be deterred by natural repugnance, and if this does not prevent you, you may perhaps be deterred by fear of passing the night hours in the company of these corpses, quartered and flayed and horrible to behold; and if this does not deter you, then perhaps you may lack the skill in drawing, essential for such representation; and if you had the skill in drawing, it may not be combined with a knowledge of perspective; and if it is so combined you may not understand the methods of geometrical demonstration and the method of estimating the forces and strength of muscles; or perhaps you may be wanting in patience so that you will not be diligent.
Concerning which things, whether or no they have all been found in me, the hundred and twenty books which I have composed will give verdict 'yes' or 'no.' In these I have not been hindered either by avarice or negligence, but only by want of time. Farewell.
source: encarta encyclopedia
How it is necessary for the painter to know the inner structure of man
The painter who has a knowledge of the nature of the sinews, muscles, and tendons will know very well in the movement of a limb how many and which of the sinews are the cause of it, and which muscle by swelling is the cause of the contraction of that sinew; and which sinews expanded into most delicate cartilage surround and support the said muscle.
Thus he will in divers ways and universally indicate the various muscles by means of the different attitudes of his figures; and will not do like many who, in a variety of movements, still display the same things in the arms, the backs, the breasts, and legs. And these things are not to be regarded as minor faults.
In fifteen entire figures there shall be revealed to you the microcosm on the same plan as before me was adopted by Ptolemy in his cosmography; and I shall divide them into limbs as he divided the macrocosm into provinces; and I shall then define the functions of the parts in every direction, placing before your eyes the representation of the whole figure of man and his capacity of movements by means of his parts. And would that it might please our Creator that I were able to reveal the nature of man and his customs even as I describe his figure.
Remember, in order to make sure of the origin of each muscle to pull the tendon produced by this muscle in such a way as to see this muscle move, and its attachment to the ligaments of the bones. You will make nothing but confusion in demonstrating the muscles and their positions, origins and ends, unless you first make a demonstration of thin muscles after the manner of threads; and in this way you will be able to represent them one over the other as nature has placed them; and thus you can name them according to the limb they serve, for instance the mover of the tip of the big toe, and of its middle bone or of the first bone, etc. And when you have given this information you will draw by the side of it the true form and size and position of each muscle; but remember to make the threads which denote the muscles in the same positions as the central line of each muscle; and so these threads will demonstrate the shape of the leg and their distance in a plain and clear manner.
source: encarta encyclopedia
The painter who has a knowledge of the nature of the sinews, muscles, and tendons will know very well in the movement of a limb how many and which of the sinews are the cause of it, and which muscle by swelling is the cause of the contraction of that sinew; and which sinews expanded into most delicate cartilage surround and support the said muscle.
Thus he will in divers ways and universally indicate the various muscles by means of the different attitudes of his figures; and will not do like many who, in a variety of movements, still display the same things in the arms, the backs, the breasts, and legs. And these things are not to be regarded as minor faults.
In fifteen entire figures there shall be revealed to you the microcosm on the same plan as before me was adopted by Ptolemy in his cosmography; and I shall divide them into limbs as he divided the macrocosm into provinces; and I shall then define the functions of the parts in every direction, placing before your eyes the representation of the whole figure of man and his capacity of movements by means of his parts. And would that it might please our Creator that I were able to reveal the nature of man and his customs even as I describe his figure.
Remember, in order to make sure of the origin of each muscle to pull the tendon produced by this muscle in such a way as to see this muscle move, and its attachment to the ligaments of the bones. You will make nothing but confusion in demonstrating the muscles and their positions, origins and ends, unless you first make a demonstration of thin muscles after the manner of threads; and in this way you will be able to represent them one over the other as nature has placed them; and thus you can name them according to the limb they serve, for instance the mover of the tip of the big toe, and of its middle bone or of the first bone, etc. And when you have given this information you will draw by the side of it the true form and size and position of each muscle; but remember to make the threads which denote the muscles in the same positions as the central line of each muscle; and so these threads will demonstrate the shape of the leg and their distance in a plain and clear manner.
source: encarta encyclopedia
Of the hand from within
When you begin the hand from within first separate all the bones a little from each other so that you may be able quickly to recognize the true shape of each bone from the palm side of the hand and also the real number and position in each finger; and have some sawn through lengthwise, so as to show which is hollow and which is full. And having done this replace the bones together at their true contacts and represent the whole hand from within wide open. The next demonstration should be of the muscles around the wrist and the rest of the hand. The fifth shall represent the tendons which move the first joints of the fingers. The sixth the tendons which move the second joints of the fingers. The seventh those which move the third joints of these fingers. The eighth shall represent the nerves which give them the sense of touch. The ninth the veins and the arteries. The tenth shall show the whole hand complete with its skin and its measurements; and measurements should also be taken of the bones. And whatever you do for this side of the hand you should also do for the other three sides—that is for the palmar side, for the dorsal side, and for the sides of the extensor and flexor muscles. And thus in the chapter on the hand you will give forty demonstrations; and you should do the same with each limb. And in this way you will attain thorough knowledge. You should afterwards make a discourse concerning the hands of each of the animals, in order to show in what way they vary. In the bear for instance the ligaments of the tendons of the toes are attached above the ankle of the foot.
Weight, force, and the motion of bodies and percussion are the four elemental powers in which all the visible actions of mortals have their being and their end.
After the demonstration of all the parts of the limbs or men and of the other animals you will represent the proper way of action of these limbs, that is in rising from lying down, in moving, running, and jumping in various attitudes, in lifting and carrying heavy weights, in throwing things to a distance, and in swimming; and in every action you will show which limbs and which muscles perform it, and deal especially with the play of the arms.
As regards the disposition of the limbs in movement you will have to consider that when you wish to represent a man who for some reason has to turn backwards or to one side you must not make him move his feet and all his limbs towards the side to which he turns his head. Rather must you make the action proceed by degrees and through the different joints, that is those of the foot, the knee, the hips, and the neck. If you set him on the right leg, you must make his left knee bend inwards and his left foot slightly raised on the outside; and let the left shoulder be somewhat lower than the right; and the nape of the neck is in a line directly over the outer ankle of the left foot. And the left shoulder will be in a perpendicular line above the toes of the right foot. And always set your figures so that the side to which the head turns is not the side to which the breast faces, since nature for our convenience has made us with a neck which bends with ease in many directions as the eye turns to various points and the other joints are partly obedient to it.
source: encarta encyclopedia
When you begin the hand from within first separate all the bones a little from each other so that you may be able quickly to recognize the true shape of each bone from the palm side of the hand and also the real number and position in each finger; and have some sawn through lengthwise, so as to show which is hollow and which is full. And having done this replace the bones together at their true contacts and represent the whole hand from within wide open. The next demonstration should be of the muscles around the wrist and the rest of the hand. The fifth shall represent the tendons which move the first joints of the fingers. The sixth the tendons which move the second joints of the fingers. The seventh those which move the third joints of these fingers. The eighth shall represent the nerves which give them the sense of touch. The ninth the veins and the arteries. The tenth shall show the whole hand complete with its skin and its measurements; and measurements should also be taken of the bones. And whatever you do for this side of the hand you should also do for the other three sides—that is for the palmar side, for the dorsal side, and for the sides of the extensor and flexor muscles. And thus in the chapter on the hand you will give forty demonstrations; and you should do the same with each limb. And in this way you will attain thorough knowledge. You should afterwards make a discourse concerning the hands of each of the animals, in order to show in what way they vary. In the bear for instance the ligaments of the tendons of the toes are attached above the ankle of the foot.
Weight, force, and the motion of bodies and percussion are the four elemental powers in which all the visible actions of mortals have their being and their end.
After the demonstration of all the parts of the limbs or men and of the other animals you will represent the proper way of action of these limbs, that is in rising from lying down, in moving, running, and jumping in various attitudes, in lifting and carrying heavy weights, in throwing things to a distance, and in swimming; and in every action you will show which limbs and which muscles perform it, and deal especially with the play of the arms.
As regards the disposition of the limbs in movement you will have to consider that when you wish to represent a man who for some reason has to turn backwards or to one side you must not make him move his feet and all his limbs towards the side to which he turns his head. Rather must you make the action proceed by degrees and through the different joints, that is those of the foot, the knee, the hips, and the neck. If you set him on the right leg, you must make his left knee bend inwards and his left foot slightly raised on the outside; and let the left shoulder be somewhat lower than the right; and the nape of the neck is in a line directly over the outer ankle of the left foot. And the left shoulder will be in a perpendicular line above the toes of the right foot. And always set your figures so that the side to which the head turns is not the side to which the breast faces, since nature for our convenience has made us with a neck which bends with ease in many directions as the eye turns to various points and the other joints are partly obedient to it.
source: encarta encyclopedia
On the grace of the limbs
The limbs should be adapted to the body with grace and with reference to the effect that you wish the figure to produce. If you wish to produce a figure that shall look light and graceful in itself you must make the limbs elegant and extended, and without too much display of the muscles; and the few that are needed you must indicate softly, that is, not very prominently and without strong shadows; the limbs and particularly the arms easy, so that they should not be in a straight line with the adjoining parts. If the hips, which are the pole of a man, are placed so that the right is higher than the left, then let the right shoulder be lower than the left and make the joint of the higher shoulder in a perpendicular line above the highest prominence of the hip. Let the pit of the throat always be over the centre of the ankle of that foot on which the man is leaning. The leg which is free should have the knee lower than the other, and near the other leg. The positions of head and arms are infinitely varied and I shall therefore not enlarge on any rules for them. Let them, however, be easy and pleasing, with various turns and twists and the joints gracefully bent, that they may not look like pieces of wood.
That is called simple movement in a man when he simply bends forward, or backwards, or to the side.
That is called a compound movement in a man when some purpose required bending down and to the side at the same time.…
source: encarta encyclopedia
The limbs should be adapted to the body with grace and with reference to the effect that you wish the figure to produce. If you wish to produce a figure that shall look light and graceful in itself you must make the limbs elegant and extended, and without too much display of the muscles; and the few that are needed you must indicate softly, that is, not very prominently and without strong shadows; the limbs and particularly the arms easy, so that they should not be in a straight line with the adjoining parts. If the hips, which are the pole of a man, are placed so that the right is higher than the left, then let the right shoulder be lower than the left and make the joint of the higher shoulder in a perpendicular line above the highest prominence of the hip. Let the pit of the throat always be over the centre of the ankle of that foot on which the man is leaning. The leg which is free should have the knee lower than the other, and near the other leg. The positions of head and arms are infinitely varied and I shall therefore not enlarge on any rules for them. Let them, however, be easy and pleasing, with various turns and twists and the joints gracefully bent, that they may not look like pieces of wood.
That is called simple movement in a man when he simply bends forward, or backwards, or to the side.
That is called a compound movement in a man when some purpose required bending down and to the side at the same time.…
source: encarta encyclopedia
Of human movement
When you wish to represent a man in the act of moving some weight reflect that these movements are to be represented in different directions. A man may stoop to lift a weight with the intention of lifting it as he straightens himself; this is a simple movement from below upwards; or he may wish to pull something backward, or push it forward or draw it down with a rope that passes over a pulley. Here you should remember that a man's weight drags in proportion as the centre of his gravity is distant from that of his support, and you must add to this the force exerted by his legs and bent spine as he straightens himself.
The sinew which guides the leg, and which is connected with the patella of the knee, feels it a greater labour to carry the man upwards in proportion as the leg is more bent; the muscle which acts upon the angle made by the thigh where it joins the body has less difficulty and less weight to lift, because it has not the weight of the thigh itself. And besides this its muscles are stronger being those which form the buttock.
The first thing that the man does when he ascends by steps is to free the leg which he wishes to raise from the weight of the trunk which is resting upon this leg, and at the same time he loads the other leg with his entire weight including that of the raised leg. Then he raises the leg and places the foot on the step where he wishes to mount; having done this he conveys to the higher foot all the weight of the trunk and of the leg and leaning his hand upon his thigh, thrusts the head forward and moves towards the point of the higher foot, while raising swiftly the heel of the lower foot; and with the impetus thus acquired he raises himself up; and at the same time by extending the arm which was resting upon his knee he pushes the trunk and head upwards and thus straightens the curve of his back.
Man and every animal undergoes more fatigue in going upwards than downwards, for as he ascends he bears his weight with him and as he descends he simply lets it go.
A man, in running, throws less of his weight on his legs than when he is standing still. In like manner the horse, when running, is less conscious of the weight of the man whom it is carrying; consequently many consider it marvellous that a horse in a race can support itself on one foot only. Therefore we may say regarding weight in transverse movement that the swifter the movement, the less the weight towards the centre of the earth.…
It is impossible that any memory can hold all the aspects and mutations of any limb of any animal. We shall demonstrate this by taking the hand for an example. Since every continuous quantity is divisible in infinitum the movement of the eye, which observes the hand, travels through a space, which is also a continuous quantity and there divisible in infinitum. And in every stage of the movement the aspect and shape of the hand varies when it is seen, and will continue to vary as the eye moves in a complete circle. And the hand in turn will act in a similar way as it is raised in its movement, that is to say it will travel through space which is a continuous quantity.
There are [four] principal simple movements in the flexion performed by the joint of the shoulder, namely when the arm attached to the same moves upward or downwards or forward or backward. One might say, though, that such movements are infinite. For if we turn our shoulder towards a wall and describe a circular figure with our arm we shall have performed all the movements contained in the said shoulder. And, since [every circle is] a continuous quantity, the movement of the arm [has produced] a continuous quantity. This movement would not produce a continuous quantity were it not guided by the principle of continuation. Therefore, the movement of that arm has been through all the parts of the circle. And as the circle is divisible in infinitum the variations of the shoulder have been infinite.
source: encarta encyclopedia
When you wish to represent a man in the act of moving some weight reflect that these movements are to be represented in different directions. A man may stoop to lift a weight with the intention of lifting it as he straightens himself; this is a simple movement from below upwards; or he may wish to pull something backward, or push it forward or draw it down with a rope that passes over a pulley. Here you should remember that a man's weight drags in proportion as the centre of his gravity is distant from that of his support, and you must add to this the force exerted by his legs and bent spine as he straightens himself.
The sinew which guides the leg, and which is connected with the patella of the knee, feels it a greater labour to carry the man upwards in proportion as the leg is more bent; the muscle which acts upon the angle made by the thigh where it joins the body has less difficulty and less weight to lift, because it has not the weight of the thigh itself. And besides this its muscles are stronger being those which form the buttock.
The first thing that the man does when he ascends by steps is to free the leg which he wishes to raise from the weight of the trunk which is resting upon this leg, and at the same time he loads the other leg with his entire weight including that of the raised leg. Then he raises the leg and places the foot on the step where he wishes to mount; having done this he conveys to the higher foot all the weight of the trunk and of the leg and leaning his hand upon his thigh, thrusts the head forward and moves towards the point of the higher foot, while raising swiftly the heel of the lower foot; and with the impetus thus acquired he raises himself up; and at the same time by extending the arm which was resting upon his knee he pushes the trunk and head upwards and thus straightens the curve of his back.
Man and every animal undergoes more fatigue in going upwards than downwards, for as he ascends he bears his weight with him and as he descends he simply lets it go.
A man, in running, throws less of his weight on his legs than when he is standing still. In like manner the horse, when running, is less conscious of the weight of the man whom it is carrying; consequently many consider it marvellous that a horse in a race can support itself on one foot only. Therefore we may say regarding weight in transverse movement that the swifter the movement, the less the weight towards the centre of the earth.…
It is impossible that any memory can hold all the aspects and mutations of any limb of any animal. We shall demonstrate this by taking the hand for an example. Since every continuous quantity is divisible in infinitum the movement of the eye, which observes the hand, travels through a space, which is also a continuous quantity and there divisible in infinitum. And in every stage of the movement the aspect and shape of the hand varies when it is seen, and will continue to vary as the eye moves in a complete circle. And the hand in turn will act in a similar way as it is raised in its movement, that is to say it will travel through space which is a continuous quantity.
There are [four] principal simple movements in the flexion performed by the joint of the shoulder, namely when the arm attached to the same moves upward or downwards or forward or backward. One might say, though, that such movements are infinite. For if we turn our shoulder towards a wall and describe a circular figure with our arm we shall have performed all the movements contained in the said shoulder. And, since [every circle is] a continuous quantity, the movement of the arm [has produced] a continuous quantity. This movement would not produce a continuous quantity were it not guided by the principle of continuation. Therefore, the movement of that arm has been through all the parts of the circle. And as the circle is divisible in infinitum the variations of the shoulder have been infinite.
source: encarta encyclopedia
One and the same action seen from various places
One and the same attitude is shown in an infinite number of variations, because it can be viewed from an infinite number of places and these places are of a continuous quantity, and a continuous quantity is divisible into an infinite number of parts. Consequently every human action shows itself in an infinite variety of situations.
The movements of man performed on one single occasion or for one single purpose are infinitely varied in themselves. This can be proved thus. Let us assume that a man strikes some object. Then I say that his stroke is made up of two states. Either he is lifting the thing which must descend in order to bring about the stroke, or this thing is already descending. Whichever may be the case, it is undeniable that the movement occurs in space and that space is a continuous quantity, and that every continuous quantity is divisible in infinitum. The conclusion is that every movement of the thing which descends is variable in infinitum.
source: encarta encyclopedia
One and the same attitude is shown in an infinite number of variations, because it can be viewed from an infinite number of places and these places are of a continuous quantity, and a continuous quantity is divisible into an infinite number of parts. Consequently every human action shows itself in an infinite variety of situations.
The movements of man performed on one single occasion or for one single purpose are infinitely varied in themselves. This can be proved thus. Let us assume that a man strikes some object. Then I say that his stroke is made up of two states. Either he is lifting the thing which must descend in order to bring about the stroke, or this thing is already descending. Whichever may be the case, it is undeniable that the movement occurs in space and that space is a continuous quantity, and that every continuous quantity is divisible in infinitum. The conclusion is that every movement of the thing which descends is variable in infinitum.
source: encarta encyclopedia
Leonardo da Vinci
In his notebooks, Renaissance artist Leonardo da Vinci recorded insights into topics as diverse as flying machines, hydrodynamics, and the human soul. He proposed a course of study for an aspiring painter, which included a thorough investigation of human anatomy. In this excerpt, Leonardo describes the measurements that led to the creation of one of his best-known drawings—a man inscribed within the dimensions of a square and a circle. Editor Irma A. Richter provides introductions to the following passages on human structure and movement from Leonardo’s notebooks.
source: Microsoft ® Encarta
THE LIFE AND STRUCTURE OF THINGS
a. Proportion
b. The anatomy and movement of the body
c. How it is necessary for the painter to know the inner structure of man
of the hand from within
on the grace of the limbs
of human movements
one and the same action seen from various places
source: Microsoft ® Encarta
THE LIFE AND STRUCTURE OF THINGS
a. Proportion
b. The anatomy and movement of the body
c. How it is necessary for the painter to know the inner structure of man
of the hand from within
on the grace of the limbs
of human movements
one and the same action seen from various places
What is the History of Anatomy?
Andreas Vesalius
Belgian anatomist and physician Andreas Vesalius helped establish the foundations of modern anatomy in the 16th century by dissecting human cadavers and publishing his results. He served as physician to Holy Roman Emperor Charles V and his son, Philip II, king of Spain. This portrait is by Dutch-born English painter Peter Lely.
The oldest known systematic study of anatomy is contained in an Egyptian papyrus dating from about 1600 bc. The treatise reveals knowledge of the larger viscera but little concept of their functions. About the same degree of knowledge is reflected in the writings of the Greek physician Hippocrates in the 5th century bc. In the 4th century bc Aristotle greatly increased anatomical knowledge of animals. The first real progress in the science of human anatomy was made in the following century by the Greek physicians Herophilus and Erasistratus, who dissected human cadavers and were the first to distinguish many functions, including those of the nervous and muscular systems. Little further progress was made by the ancient Romans or by the Arabs. The Renaissance first influenced the science of anatomy in the latter half of the 16th century.
Modern anatomy began with the publication in 1543 of the work of the Belgian anatomist Andreas Vesalius. Before the publication of this classical work anatomists had been so bound by tradition that the writings of authorities of more than 1000 years earlier, such as the Greek physician Galen, who had been restricted to the dissection of animals, were accepted in lieu of actual observation. Vesalius and other Renaissance anatomists, however, based their descriptions on their own observations of human corpses, thus setting the pattern for subsequent study in anatomy.
Source: encarta encyclopedia
Belgian anatomist and physician Andreas Vesalius helped establish the foundations of modern anatomy in the 16th century by dissecting human cadavers and publishing his results. He served as physician to Holy Roman Emperor Charles V and his son, Philip II, king of Spain. This portrait is by Dutch-born English painter Peter Lely.
The oldest known systematic study of anatomy is contained in an Egyptian papyrus dating from about 1600 bc. The treatise reveals knowledge of the larger viscera but little concept of their functions. About the same degree of knowledge is reflected in the writings of the Greek physician Hippocrates in the 5th century bc. In the 4th century bc Aristotle greatly increased anatomical knowledge of animals. The first real progress in the science of human anatomy was made in the following century by the Greek physicians Herophilus and Erasistratus, who dissected human cadavers and were the first to distinguish many functions, including those of the nervous and muscular systems. Little further progress was made by the ancient Romans or by the Arabs. The Renaissance first influenced the science of anatomy in the latter half of the 16th century.
Modern anatomy began with the publication in 1543 of the work of the Belgian anatomist Andreas Vesalius. Before the publication of this classical work anatomists had been so bound by tradition that the writings of authorities of more than 1000 years earlier, such as the Greek physician Galen, who had been restricted to the dissection of animals, were accepted in lieu of actual observation. Vesalius and other Renaissance anatomists, however, based their descriptions on their own observations of human corpses, thus setting the pattern for subsequent study in anatomy.
Source: encarta encyclopedia
Know the metabolism of Cardiac Muscles
Cardiac muscle is adapted to be highly resistant to fatigue: it has a large number of mitochondria, enabling continuous aerobic respiration, numerous myoglobins (oxygen-storing pigment), and a good blood supply, which provides nutrients and oxygen. The heart is so tuned to aerobic metabolism that it is unable to pump sufficiently in ischaemic conditions. At basal metabolic rates, about 1% of energy is derived from anaerobic metabolism. This can increase to 10% under moderately hypoxic conditions, but, under more severe hypoxic conditions, not enough energy can be liberated by lactate production to sustain ventricular contractions.
Under basal aerobic conditions, 60% of energy comes from fat (free fatty acids and triacylglycerols/triglycerides), 35% from carbohydrates, and 5% from amino acids and ketone bodies. However, these proportions vary widely according to nutritional state. For example, during starvation, lactate can be recycled by the heart. This is very energy efficient, because one NAD+ is reduced to NADH and H+ (equal to 2.5 or 3 ATP) when lactate is oxidized to pyruvate, which can then be burned aerobically in the TCA cycle, liberating much more energy (ca 14 ATP per cycle).
In the condition of diabetes, more fat and less carbohydrate is used due to the reduced induction of GLUT4 glucose transporters to the cell surfaces. However, contraction itself plays a part in bringing GLUT4 transporters to the surface.This is true of skeletal muscle, but relevant in particular to cardiac muscle, since it is always contracting.
Unlike skeletal muscle, which contracts in response to nerve stimulation, specialized pacemaker cells at the entrance of the right atrium termed the sinoatrial node display the phenomenon of automaticity and are myogenic, meaning that they are self-excitable without a requisite electrical impulse coming from the central nervous system. The rest of the myocardium conducts these action potentials by way of electrical synapses called gap junctions. It is because of this automaticity that an individual's heart does not stop when a neuromuscular blocker (such as succinylcholine or rocuronium) is administered, such as during general anesthesia.
A single cardiac muscle cell, if left without input, will contract rhythmically at a steady rate; if two cardiac muscle cells are in contact, whichever one contracts first will stimulate the other to contract, and so on. This inherent contractile activity is heavily regulated by the autonomic nervous system. If synchronization of cardiac muscle contraction is disrupted for some reason (for example, in a heart attack), uncoordinated contraction known as fibrillation can result.
source: wikipedia encyclopedia
Under basal aerobic conditions, 60% of energy comes from fat (free fatty acids and triacylglycerols/triglycerides), 35% from carbohydrates, and 5% from amino acids and ketone bodies. However, these proportions vary widely according to nutritional state. For example, during starvation, lactate can be recycled by the heart. This is very energy efficient, because one NAD+ is reduced to NADH and H+ (equal to 2.5 or 3 ATP) when lactate is oxidized to pyruvate, which can then be burned aerobically in the TCA cycle, liberating much more energy (ca 14 ATP per cycle).
In the condition of diabetes, more fat and less carbohydrate is used due to the reduced induction of GLUT4 glucose transporters to the cell surfaces. However, contraction itself plays a part in bringing GLUT4 transporters to the surface.This is true of skeletal muscle, but relevant in particular to cardiac muscle, since it is always contracting.
Unlike skeletal muscle, which contracts in response to nerve stimulation, specialized pacemaker cells at the entrance of the right atrium termed the sinoatrial node display the phenomenon of automaticity and are myogenic, meaning that they are self-excitable without a requisite electrical impulse coming from the central nervous system. The rest of the myocardium conducts these action potentials by way of electrical synapses called gap junctions. It is because of this automaticity that an individual's heart does not stop when a neuromuscular blocker (such as succinylcholine or rocuronium) is administered, such as during general anesthesia.
A single cardiac muscle cell, if left without input, will contract rhythmically at a steady rate; if two cardiac muscle cells are in contact, whichever one contracts first will stimulate the other to contract, and so on. This inherent contractile activity is heavily regulated by the autonomic nervous system. If synchronization of cardiac muscle contraction is disrupted for some reason (for example, in a heart attack), uncoordinated contraction known as fibrillation can result.
source: wikipedia encyclopedia
Discover the functions of Muscles
Smooth muscle is found in organs made up also of other tissues, such as the heart and intestines, which contain layers of connective tissue.
Skeletal muscle is usually found in bundles, composing muscular structures resembling organs in function.
These often ripple the skin visibly during muscular action.
The shape of the muscular organ is dependent on its location and function.
Such a muscle structure is named scientifically according to its shape, function, or attachments: the trapezius muscle of the back, for example, is so called because it looks like a geometrical figure known as a trapezoid; and the masseter (Greek masētēr, “a chewer”) muscle of the face is so called because it is used in chewing food.
Muscle fibers have been classified by function into slow twitch (type I) and fast twitch (type II). Most skeletal muscles are composed of both types of fibers, although one type may predominate. The fast-twitch, darker-hued muscle fibers contract more rapidly and produce bursts of power; the slow-twitch, lighter-hued muscle fibers have greater endurance.
Contraction of a muscle cell is activated by the release of calcium from inside the cell, probably in response to electrical changes at the cell's surface. See Anatomy.
Muscles that are given proper exercise react to stimuli quickly and powerfully, and are said to possess tone. As a result of excessive use, muscles may hypertrophy, that is, increase in size because of an increase in size of the individual muscle cells.
As a result of prolonged disuse, muscles may atrophy, or diminish in size, and become weaker. In certain diseases, such as various forms of paralysis, the muscles may atrophy to such a degree that they are reduced to a fraction of their normal size.
Skeletal muscle is usually found in bundles, composing muscular structures resembling organs in function.
These often ripple the skin visibly during muscular action.
The shape of the muscular organ is dependent on its location and function.
Such a muscle structure is named scientifically according to its shape, function, or attachments: the trapezius muscle of the back, for example, is so called because it looks like a geometrical figure known as a trapezoid; and the masseter (Greek masētēr, “a chewer”) muscle of the face is so called because it is used in chewing food.
Muscle fibers have been classified by function into slow twitch (type I) and fast twitch (type II). Most skeletal muscles are composed of both types of fibers, although one type may predominate. The fast-twitch, darker-hued muscle fibers contract more rapidly and produce bursts of power; the slow-twitch, lighter-hued muscle fibers have greater endurance.
Contraction of a muscle cell is activated by the release of calcium from inside the cell, probably in response to electrical changes at the cell's surface. See Anatomy.
Muscles that are given proper exercise react to stimuli quickly and powerfully, and are said to possess tone. As a result of excessive use, muscles may hypertrophy, that is, increase in size because of an increase in size of the individual muscle cells.
As a result of prolonged disuse, muscles may atrophy, or diminish in size, and become weaker. In certain diseases, such as various forms of paralysis, the muscles may atrophy to such a degree that they are reduced to a fraction of their normal size.
Know the Cardiac muscles
The cardiac muscle (photo)is a type of involuntary striated muscle found in the walls of the heart. As it contracts, it propels blood into the heart and through the blood vessels of the circulatory system.
Cardiac Muscle Cardiac muscle, found only in the heart, drives blood through the circulatory system. Cardiac muscle cells connect to each other by specialized junctions called intercalated disks. Without a constant supply of oxygen, cardiac muscle will die, and heart attacks occur from the damage caused by insufficient blood supply to cardiac muscle.
This muscle tissue composes most of the vertebrate heart. The cells, which show both longitudinal and imperfect cross striations, differ from skeletal muscle primarily in having centrally placed nuclei and in the branching and interconnecting of fibers.
Cardiac muscle is not under voluntary control. It is supplied with nerves from the autonomic nervous system, but autonomic impulses merely speed or slow its action and are not responsible for the continuous rhythmic contraction characteristic of living cardiac muscle. The mechanism of cardiac contraction is not yet understood.
source: wiki/encarta encyclopedia
Know the Skeletal, or Striated, Muscle tissue
Striated muscle is a form of fibres that are separated into parallel fibres
Skeletal muscle (photo) enables the voluntary movement of bones. Skeletal muscle consists of densely packed groups of elongated cells known as muscle fibers. Within these fibers, the alternation of thick and thin myofilaments gives skeletal muscles a striated, or striped, appearance.
This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations. Skeletal muscle is supplied with nerves from the central nervous system, and because it is partly under conscious control, it is also called voluntary muscle. Most skeletal muscle is attached to portions of the skeleton by connective-tissue attachments called tendons. Contractions of skeletal muscle serve to move the various bones and cartilages of the skeleton. Skeletal muscle forms most of the underlying flesh of vertebrates.
This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations. Skeletal muscle is supplied with nerves from the central nervous system, and because it is partly under conscious control, it is also called voluntary muscle. Most skeletal muscle is attached to portions of the skeleton by connective-tissue attachments called tendons. Contractions of skeletal muscle serve to move the various bones and cartilages of the skeleton. Skeletal muscle forms most of the underlying flesh of vertebrates.
source: wiki/encarta encyclopedia
Know the Smooth muscles
Smooth muscle (photo) is a type of non-striated muscle, found within the tunica media layer of arteries and veins, the bladder, uterus, male and female reproductive tracts, gastrointestinal tract, respiratory tract, the ciliary muscle, and iris of the eye.The glomeruli of the kidneys contain a smooth muscle-like cell called the mesangial cell. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, excitation-contraction coupling, and mechanism of contraction.
Smooth Muscle Human smooth muscle is composed of slender, spindle-shaped cells, each with a single nucleus. Smooth muscle cells contract in rhythmic waves to propel food through the digestive tract and provide tension in the urinary bladder, blood vessels, uterus, and other internal organs.
Muscle is composed of spindle-shaped cells, each having a central nucleus. The cells have no cross striations, although they do exhibit faint longitudinal striations. Stimuli for the contractions of smooth muscles are mediated by the autonomic nervous system. Smooth muscle is found in the skin, internal organs, reproductive system, major blood vessels, and excretory system.
source:wiki/encarta encyclopedia
know the Organization anthropod
A: Cuticle and Epidermis:
Epicuticle detail .
1: Epicuticle
1a: Cement layer;
1b: Wax layer;
1c: Outer epicuticle;
1d: Inner epicuticle.
2: Exocuticle
3: Endocuticle
2+3: Procuticle
4: Epidermis
5: Basement membrane
6: epi. cell
6a: Pore canal
7: Glandular cell
8: Trichogen cell
9: Tormogen cell
10: Nerve
11: Sensilia
12: Hair
13: Gland opening.
Epicuticle detail .
1: Epicuticle
1a: Cement layer;
1b: Wax layer;
1c: Outer epicuticle;
1d: Inner epicuticle.
2: Exocuticle
3: Endocuticle
2+3: Procuticle
4: Epidermis
5: Basement membrane
6: epi. cell
6a: Pore canal
7: Glandular cell
8: Trichogen cell
9: Tormogen cell
10: Nerve
11: Sensilia
12: Hair
13: Gland opening.
Know the Natural exoskeleton
The relative rigidity of the exoskeleton means that continuous growth of arthropods is not possible. Therefore, growth is periodic and concentrated into a period of time when the exoskeleton is shed, called moulting or ecdysis, which is under the control of a hormone called ecdysone. Moulting is a complex process that is invariably dangerous for the arthropod involved. Before the old exoskeleton is shed, the cuticle separates from the epidermis through a process called apolysis. New cuticle is excreted by the underlying epidermis, and mineral salts are usually withdrawn from the old cuticle for re-use. After the old cuticle is shed, the arthropod typically pumps up its body (for example, by air or water intake) to allow the new cuticle to expand to a larger size: the process of hardening by dehydration of the cuticle then takes place. Newly molted arthropods typically appear pale or white, and darken as the cuticle hardens.
Know the Microscopic structure
A typical arthropod exoskeleton is a multi-layered structure with four functional regions: epicuticle, procuticle, epidermis and basement membrane,the epicuticle is a multi-layered external barrier that, especially in terrestrial arthropods, acts as a barrier against dessiccation. The strength of the exoskeleton is provided by the underlying procuticle, which is in turn secreted by the epidermis. Arthropod cuticle is a biological composite material, consisting of two main portions: fibrous chains of alpha-chitin within a matrix of silk-like and globular proteins, of which the most well-known is the rubbery protein called resilin. The relative abundance of these two main components varies from approximately 50/50 to 70/30 protein/chitin, with softer parts of the exoskeleton having a higher proportion of chitin. Although the cuticle is relatively soft when first secreted, it soon hardens in a poorly-understood process that involves dehydration and/or tanning mediated by hydrophobic chemicals called phenolics. Different types of interaction between the proteins and chitin leads to varying mechanical properties of the exoskeleton.In addition to the chitino-proteinaceous composite of the cuticle, many crustaceans, some myriapods and the extinct trilobites further impregnate the cuticle with mineral salts, above all calcium carbonate, which can make up up to 40% of the cuticle. This can lead to great mechanical strength.
know the ECDYSIS
The progression of ecdysis in Callinectes sapidus, the blue crab.
Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). Since the cuticula of these animals is also the skeletal support (the exoskeleton) of the body and is inelastic, it is shed during growth and a new, larger covering is formed. The old, empty exoskeleton is called an exuvia (or "exuvium").
After molting, an arthropod is described as teneral; it is "fresh", pale and soft-bodied. Within one or two hours, the cuticle hardens and darkens following a tanning process similar to that of the tanning of leather. It is during this short phase that the animal grows, since growth is otherwise constrained by the rigidity of the exoskeleton.
Ecdysis may also enable damaged tissue and missing limbs to be regenerated or substantially re-formed, although this may only be complete over a series of molts, the stump being a little larger with each molt until it is of normal, or near normal size again.
Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). Since the cuticula of these animals is also the skeletal support (the exoskeleton) of the body and is inelastic, it is shed during growth and a new, larger covering is formed. The old, empty exoskeleton is called an exuvia (or "exuvium").After molting, an arthropod is described as teneral; it is "fresh", pale and soft-bodied. Within one or two hours, the cuticle hardens and darkens following a tanning process similar to that of the tanning of leather. It is during this short phase that the animal grows, since growth is otherwise constrained by the rigidity of the exoskeleton.
Ecdysis may also enable damaged tissue and missing limbs to be regenerated or substantially re-formed, although this may only be complete over a series of molts, the stump being a little larger with each molt until it is of normal, or near normal size again.
What is Endoskeleton?
An endoskeleton is an internal support structure of an animal. In three phyla and one subclass of animals, endoskeletons of various complexity are found: Chordata, Echinodermata, Porifera, and Coleoidea. An endoskeleton allows the body to move and gives the body structure and shape. A true endoskeleton is derived from mesodermal tissue. Such a skeleton is present in echinoderms and chordates. The poriferan 'skeleton' consists of microscopic calcareous or siliceous spicules or a spongin network. The Coleoidae do not have a true endoskeleton in the evolutionary sense; here, a mollusc exoskeleton evolved into several sorts of internal structure, the "cuttlebone" of cuttlefish being the best-known version. Yet they do have cartilaginous tissue in their body, even if it is not mineralized, especially in the head, where it forms a primitive cranium. An important advantage of an endoskeleton over an exoskeleton is that it provides more structural support.
Vertebrates have a more or less rigid group of structures composed of cartilage or bone or of a combination of these two connective tissues. The most primitive of these structures is the notochord, which is a backbone of cartilage occurring in fishes. Animals higher on the evolutionary scale have an axial skeleton, consisting of the skull, spinal column, and ribs, and an appendicular skeleton, made up of the pelvic and pectoral girdles and the appendages.
source: wiki/encarta encyclopedia
Vertebrates have a more or less rigid group of structures composed of cartilage or bone or of a combination of these two connective tissues. The most primitive of these structures is the notochord, which is a backbone of cartilage occurring in fishes. Animals higher on the evolutionary scale have an axial skeleton, consisting of the skull, spinal column, and ribs, and an appendicular skeleton, made up of the pelvic and pectoral girdles and the appendages.
source: wiki/encarta encyclopedia
What is Exoskeleton?
An exoskeleton is a type of skeleton that is an external anatomical feature that supports and protects an animal's body, in contrast to the internal endoskeleton of, for example, a human. Whilst many, many other invertebrate animals (such as shelled mollusks) have exoskeletons in the sense of external hard parts, the characteristic is most associated with the arthropods (i.e. insects, spiders, myriapods and crustaceans). Exoskeletons contain rigid and resistant components that fulfil a set of functional roles including protection, excretion, sensing, support, feeding and (for terrestrial organisms) acting as a barrier against desiccation. Exoskeletons first appeared in the fossil record about 550 million years ago, and their evolution has been seen as a critical driving role in the Cambrian explosion of animals that took place subsequent to this time.
A form of exoskeleton is the shell of calcium or silica secreted by certain protozoans known as foraminiferans. Commercial sponges have an exoskeleton consisting of spongin, which is a tough, elastic substance. Cnidarians secrete a wide variety of exoskeletal substances, ranging from the elastic covering of the jellyfish to the stony material deposited by coral. The familiar shells of most mollusks are composed of calcium carbonate and an organic ground substance known as conchiolin. Among insects, each of the three principal divisions of the body—the head, the thorax, and the abdomen—is enclosed in a framework of horny plates. The plates of each primary division are separated from those of the next division by elastic tissue that permits flexibility of motion. The appendages are enclosed by sheaths projecting from the exoskeleton; elastic tissue similar to that between the plates joins the segments of the appendages and attaches them to the body.
source: wiki/encarta encyclopedia
A form of exoskeleton is the shell of calcium or silica secreted by certain protozoans known as foraminiferans. Commercial sponges have an exoskeleton consisting of spongin, which is a tough, elastic substance. Cnidarians secrete a wide variety of exoskeletal substances, ranging from the elastic covering of the jellyfish to the stony material deposited by coral. The familiar shells of most mollusks are composed of calcium carbonate and an organic ground substance known as conchiolin. Among insects, each of the three principal divisions of the body—the head, the thorax, and the abdomen—is enclosed in a framework of horny plates. The plates of each primary division are separated from those of the next division by elastic tissue that permits flexibility of motion. The appendages are enclosed by sheaths projecting from the exoskeleton; elastic tissue similar to that between the plates joins the segments of the appendages and attaches them to the body.
source: wiki/encarta encyclopedia
What is skeleton ?
In biology, the skeleton or skeletal system is a strong framework that supports the body. External rigid frameworks, such as those found in some invertebrates (e.g. insects), are termed exoskeletons. Internal rigid frameworks, such as those found in most vertebrates (e.g. mammals), are termed endoskeletons.
The average adult human skeleton has around 206 bones These bones meet at joints, the majority of which are freely movable, making the skeleton flexible and mobile. The skeleton also contains cartilage for elasticity. Ligaments are strong strips of fibrous connective tissue that hold bones together at joints, thereby stabilizing the skeleton during movement.
Skeleton (anatomy), term applied to all the rigid or semirigid structures supporting the soft tissues of an animal's body and providing leverage for muscular action. In vertebrates, the skeleton is known as the endoskeleton and is formed within the body. Some invertebrate animals, such as insects and crustaceans, have skeletons known as exoskeletons on the outside of the body.
source: wiki/encarta encyclopedia
What is Muscle ?
Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell.
They are classified as:
skeletal cardiac or smooth muscles.
Their function is to produce force and cause motion. Muscles can cause either locomotion of the organism itself or movement of internal organs. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples are the contraction of the heart and peristalsis which pushes food through the digestive system.
Voluntary contraction of the skeletal muscles is used to move the body and can be finely controlled. Examples are movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers: slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force.
fast twitch fibers contract quickly and powerfully but fatigue very rapidly.
Muscle, tissue or organ of the animal body characterized by the ability to contract, usually in response to a stimulus from the nervous system. The basic unit of all muscle is the myofibril, a minute, threadlike structure composed of complex proteins. Each muscle cell, or fiber, contains several myofibrils, which are composed of regularly arranged myofilaments of two types, thick and thin. Each thick myofilament contains several hundred molecules of the protein myosin. Thin filaments contain two strands of the protein actin. The myofibrils are made up of alternating rows of thick and thin myofilaments with their ends interleaved. During muscular contractions, these interdigitated rows of filaments slide along each other by means of cross bridges that act as ratchets. The energy for this motion is generated by densely packed mitochondria that surround the myofibrils.
source: wiki/encarta encyclopedia
They are classified as:
skeletal cardiac or smooth muscles.
Their function is to produce force and cause motion. Muscles can cause either locomotion of the organism itself or movement of internal organs. Cardiac and smooth muscle contraction occurs without conscious thought and is necessary for survival. Examples are the contraction of the heart and peristalsis which pushes food through the digestive system.
Voluntary contraction of the skeletal muscles is used to move the body and can be finely controlled. Examples are movements of the eye, or gross movements like the quadriceps muscle of the thigh. There are two broad types of voluntary muscle fibers: slow twitch and fast twitch. Slow twitch fibers contract for long periods of time but with little force.
fast twitch fibers contract quickly and powerfully but fatigue very rapidly.
Muscle, tissue or organ of the animal body characterized by the ability to contract, usually in response to a stimulus from the nervous system. The basic unit of all muscle is the myofibril, a minute, threadlike structure composed of complex proteins. Each muscle cell, or fiber, contains several myofibrils, which are composed of regularly arranged myofilaments of two types, thick and thin. Each thick myofilament contains several hundred molecules of the protein myosin. Thin filaments contain two strands of the protein actin. The myofibrils are made up of alternating rows of thick and thin myofilaments with their ends interleaved. During muscular contractions, these interdigitated rows of filaments slide along each other by means of cross bridges that act as ratchets. The energy for this motion is generated by densely packed mitochondria that surround the myofibrils.
source: wiki/encarta encyclopedia
The Musculoskeletal System of the body
The human skeleton consists of more than 200 bones bound together by tough and relatively inelastic connective tissues called ligaments. The different parts of the body vary greatly in their degree of movement. Thus, the arm at the shoulder is freely movable, whereas the knee joint is definitely limited to a hingelike action. The movements of individual vertebrae are extremely limited; the bones composing the skull are immovable. Movements of the bones of the skeleton are effected by contractions of the skeletal muscles, to which the bones are attached by tendons. These muscular contractions are controlled by the nervous system.
What is anatomy?
Anatomy (Greek anatomē, “dissection”)
Is branch of natural science dealing with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. For centuries anatomical knowledge consisted largely of observations of dissected plants and animals. The proper understanding of structure, however, implies a knowledge of function in the living organism.
Anatomy is therefore almost inseparable from physiology, which is sometimes called functional anatomy. As one of the basic life sciences, anatomy is closely related to medicine and to other branches of biology.
It is convenient to subdivide the study of anatomy in several different ways. One classification is based on the type of organisms studied, the major subdivisions being plant anatomy and animal anatomy. Animal anatomy is further subdivided into human anatomy and comparative anatomy, which seeks out similarities and differences among animal types.
Anatomy can also be subdivided into biological processes.
For example:
Developmental anatomy- the study of embryos
Pathological anatomy- the study of diseased organs.
Other subdivisions:
Surgical anatomy
Anatomical art
Are based on the relationship of anatomy to other branches of activity under the general heading of applied anatomy. Still another way to subdivide anatomy is by the techniques employed
For example:
Microanatomy, which concerns itself with observations made with the help of the microscope.
source: encarta encyclopedia
Is branch of natural science dealing with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. For centuries anatomical knowledge consisted largely of observations of dissected plants and animals. The proper understanding of structure, however, implies a knowledge of function in the living organism.
Anatomy is therefore almost inseparable from physiology, which is sometimes called functional anatomy. As one of the basic life sciences, anatomy is closely related to medicine and to other branches of biology.
It is convenient to subdivide the study of anatomy in several different ways. One classification is based on the type of organisms studied, the major subdivisions being plant anatomy and animal anatomy. Animal anatomy is further subdivided into human anatomy and comparative anatomy, which seeks out similarities and differences among animal types.
Anatomy can also be subdivided into biological processes.
For example:
Developmental anatomy- the study of embryos
Pathological anatomy- the study of diseased organs.
Other subdivisions:
Surgical anatomy
Anatomical art
Are based on the relationship of anatomy to other branches of activity under the general heading of applied anatomy. Still another way to subdivide anatomy is by the techniques employed
For example:
Microanatomy, which concerns itself with observations made with the help of the microscope.
source: encarta encyclopedia
What is Human anatomy?
Human anatomy
Is primarily the scientific study of the morphology of the adult human body.
Anatomy is subdivided into :
1. gross anatomy 2. microscopic anatomy.
Group I
a.) Gross anatomy
b.) Topographical anatomy,
c.) regional anatomy, or anthropotomy)
These are the study of anatomical structures that can be seen by unaided vision.
Group II
Microscopic anatomy which includes:
a.) histology (the study of the organization of tissues)
b.) cytology (the study of cells).
c.) Anatomy, physiology (the study of function)
d.) biochemistry (the study of the chemistry of living structures)
These are the study of minute anatomical structures assisted with microscopes,
are complementary basic medical sciences which are usually taught together (or in tandem).
In some of its facets human anatomy is closely related to embryology, comparative anatomy and comparative embryology through common roots in evolution; for example, much of the human body maintains the ancient segmental pattern that is present in all vertebrates with basic units being repeated, which is particularly obvious in the vertebral column and in the ribcage, and can be traced from very early embryos.
The human body consists of biological systems, that consist of organs, that consist of tissues, that consist of cells and connective tissue.
The history of anatomy has been characterized, over time, by a continually developing understanding of the functions of organs and structures in the body. Methods have also advanced dramatically, advancing from examination of animals through dissection of preserved cadavers (dead human bodies) to technologically complex techniques developed in the 20th century.
source: wikipedia
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