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