. Human physiology : designed for colleges and the higher classes in schools, and for general reading. y I 1° rangement. The movement performed ^^^^r W by this muscle is throwing the leg and -i ^ ■ ■ V 1/foot forward, which it is by the above I iff arrangement of the patella enabled to V Wf do with great ease in walking, and \ V with great force in the act of kicking. \ 305. The pulley is used in the ar- \ rangement of the muscles, though byno means as often as the lever. Itserves, whenever it is used, to give the force a different direction is 206 HUMAN PHYSIOLOGY. The pulley-arrangement in m
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. y I 1° rangement. The movement performed ^^^^r W by this muscle is throwing the leg and -i ^ ■ ■ V 1/foot forward, which it is by the above I iff arrangement of the patella enabled to V Wf do with great ease in walking, and \ V with great force in the act of kicking. \ 305. The pulley is used in the ar- \ rangement of the muscles, though byno means as often as the lever. Itserves, whenever it is used, to give the force a different direction is 206 HUMAN PHYSIOLOGY. The pulley-arrangement in muscles. from what it would otherwise have. I will cite but a fewexamples. At the wrist and the ankle there are broad liga-ments, which bind down the tendons of the muscles, and sus-tain to them the relation of pullies. If it were not for theseligaments the tendons at these joints would fly out continuallywhen the muscles are in action, making projecting cords underthe skin. And if the skin were removed, the tendons wouldbe in a position similar to that represented at A, in Fig. 119. FIG. In this Figure, C is the tendon of the great toe in its position asbound down by ligaments. Now if the muscle were in theposition represented by A, it is plain that it would act at agreater mechanical advantage than in the position C; but thetoe would not be moved as quickly; and besides, if the tendonsprojected in this way, the foot would be a very cumbrous pieceof machinery, compared with what it is now, with the tendonsbound down around the slender ankle. So that both beautyand use are secured by the arrangement. 306. There is a beautiful application of the pulley in thecase of the muscle that draws down the lower jaw, calledthe digastric muscle. It is represented in Fig. 120, in whicha is one end of the muscle attached behind the ear, and b is theother end attached to the inside of the lower part of the chin. THE MUSCLES. 207 Manner in wliich the lower jaw is drawn down. FIG. 120
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