Page:Popular Science Monthly Volume 42.djvu/776

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borne, and the unfortunate youth, is forced by it to leave the study of medicine and turn his attention to some easier pursuit.

Now, I think that with a little trouble one may find a way of linking anatomical relationships together in a more rational way than that of "Bodfi," a word which in my student days was usedPSM V42 D776 Diagram of shoulder joint.jpgFig. 6.-Diagram of Shoulder Joint, to show the capsule. as a mnemonic to describe the form of the hippocampal convolution of the brain—backward, outward, downward, forward, and inward. The word also served to describe the course of the ribs, but Dr. Anderson Stewart has shown us how naturally the peculiar twist the ribs take in a man arises from his upright position. Taking a circular steel hoop, and simply hanging it up by one side, he shows that it assumes an oval shape, like that of the thorax of animals going upon four legs and whose ribs hang vertically from the spine. On raising this up by one point it becomes twisted upon itself and takes precisely the peculiar bend which the ribs possess in man. The advantage of a naturally jointed skeleton is so obvious that I need not further discuss it here, nor need I discuss the texture of bone which has been so admirably treated of by my friend Dr. Donald Macalister, of Cambridge (Fig. 5).

The ligaments and the joints were to me most puzzling until Dr. Joseph Bell pointed out to me how very simple they were. PSM V42 D776 Diagram of ligaments of phalanges.jpgFig. 7.—Diagram of Ligaments of Phalanges—a capsule and lateral ligaments. What is wanted in a joint is a capsule to go round it so as to hold the ends of the bones together and prevent the synovial fluid from oozing out. If the bones have to move freely in all directions they must have a ball-and-socket joint, as at the shoulder (Fig. 6) and at the hip, and there you will have a simple capsule because it can not be particularly strengthened at one point or another without interfering with freedom of movement. In the case of a hinge-joint, such as those of the fingers or toes, elbows or knees, you will have the capsule remaining thin at the front and back so as to leave the movement free, but you will have it strengthened at the sides so as to tie (Fig. 7) the bones more firmly together, and the stronger parts are called lateral ligaments. If several bones have to be connected, each one must be tied first of all to the one nearest it, and then two or three must be tied together at a time, and in this way we get the network of ligaments which we find at the wrist and tarsus (Fig. 8). The same thing is true