. Human physiology : designed for colleges and the higher classes in schools, and for general reading. F being the fulcrum, the power in raising the weight, W, to c,if acting at P, passes through the space indicated by the dottedline a. But if it act at p, it will pass through all the space b,and of course raise the weight more slowly than when acting at Most of the muscles work at a mechanical disadvantagein another way. I refer to the direction in which the muscleacts on the bone to be moved. This is seldom at right angles,and therefore a considerable part of the force exerted is lost
. Human physiology : designed for colleges and the higher classes in schools, and for general reading. F being the fulcrum, the power in raising the weight, W, to c,if acting at P, passes through the space indicated by the dottedline a. But if it act at p, it will pass through all the space b,and of course raise the weight more slowly than when acting at Most of the muscles work at a mechanical disadvantagein another way. I refer to the direction in which the muscleacts on the bone to be moved. This is seldom at right angles,and therefore a considerable part of the force exerted is can be made clear to you by Fig. 115. Let b representthe bone of the arm, and r its fulcrum, or point of support inthe shoulder. You readily see that if the bone be acted on bya muscle, m, at right-angles to it, it will require less force tomove it to a given point than would be required if the samemuscle were placed in the position represented by n. For the 204 HIMAN PHYSIOLOGY. When !os8 in power, gain in muscle n, acting obliquely on the bone would expend a part ofits force in pressing the end of the bone upward against thesocket of the joint at r. 303. But in this case also, what is lost in power is gained inquickness of movement. This can be shown on the will suppose that the? muscle contracts or shortens itself thehalf of the length of the teiHon. If the muscle were placed asat m, the bone would be carried to the line a, c. But if themuscle be placed as at n, the same degree of contraction wouldraise the bone to the line a, d, the point of the bone where thetendon of the muscle is attached moving in the curved line asmarked. The resistance to be overcome, of course, requiresmuch more power for the obliquely placed muscle, w, to raisethe bone to the line a, d, than for the muscle m to raise it toa, c; and therefore a much larger muscle is needed than therewould be if it acted at right-angles to the bone as at m. Andthe muscle which raises the ar
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