. Human physiology : designed for colleges and the higher classes in schools, and for general reading. ones the power is applied quite near to the fulcrum. Thetendon of the biceps, as you see, is fastened to the main boneof the forearm near the fulcrum, the elbow. You can readilysee that the point where the power is applied would passthrough but a little space, in moving a weight through a con-siderable one. The lower jaw, in its upward motion, is a leverof the same kind. In this case, force rather than quickness isrequired in breaking and grinding the food. Here, therefore,th
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. ones the power is applied quite near to the fulcrum. Thetendon of the biceps, as you see, is fastened to the main boneof the forearm near the fulcrum, the elbow. You can readilysee that the point where the power is applied would passthrough but a little space, in moving a weight through a con-siderable one. The lower jaw, in its upward motion, is a leverof the same kind. In this case, force rather than quickness isrequired in breaking and grinding the food. Here, therefore,the power, the action of the muscle, is applied farther fromthe fulcrum than in the case of the biceps muscle of the arm, 202 HUMAN PHYSIOLOGY. Force most important in the case of the lower jnw. and nearer to the weight to be moved, or the point where theresistance is which is to be overcome. It is applied also in adifferent direction, a point which I shall however speak of inanother connection. The muscles which move the lower jawupward can be seen in Fig. 113. One is the large spreading FIG. MUSCLES OY FACE AND NECK. muscle b, the swelling of which, in its contraction, we can feel,if we place the fingers on the temple while moving the lowerjaw upward. The other is the short strong muscle c, the frontedge of which is so far forward, that one-third at least of thelower jaw-bone is embraced by this muscle. Now, if you com-pare this bone as a lever with the forearm as acted upon bythe biceps, you will at once see that the power is applied muchnearer to the weight, or the resistance to be overcome, in thecase of the jaw, than in the case of the arm. It is so even whenthe resistance to be overcome is at the front teeth; and it ismuch more so when the resistance is at the back part of themouth, as when we are grinding our food. Here, indeed, a por-tion of the muscular force is brought to bear upon the resistancein a direct line. It is not merely because the back teeth aro THE MU
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