. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. MUSCULAR AND SKELETAL SYSTEMS. 229 Or take the case of the deltoid holding a weight at arm's length (Fig. 147). I suppose a man of good mus- cular vigor will hold at arm's length a weight of thirty Fig. 147.—Diagram showing the power of the deltoid in raising ,-y) the arm. ' ' gastr pounds. Now, in order to do so, the deltoid taking hold at four inches from the fulcrum, /, and the weight held at two feet from the same, if it pulled directly upward it would have to pull with a forc
. Outlines of the comparative physiology and morphology of animals. Anatomy, Comparative; Physiology, Comparative. MUSCULAR AND SKELETAL SYSTEMS. 229 Or take the case of the deltoid holding a weight at arm's length (Fig. 147). I suppose a man of good mus- cular vigor will hold at arm's length a weight of thirty Fig. 147.—Diagram showing the power of the deltoid in raising ,-y) the arm. ' ' gastr pounds. Now, in order to do so, the deltoid taking hold at four inches from the fulcrum, /, and the weight held at two feet from the same, if it pulled directly upward it would have to pull with a force of 30 x 6 = 180 pounds. But it pulls at a small angle, and we must multiply this again by at least four—i. e., 180 X 4 = 720 pounds. Or take one more—viz., the case of the rocnemius and soleus muscles (the calf the leg) lifting the heel. I suppose any son of ordinary weight and vigor can e another person of average weight, one hundred and fifty pounds, on his back, making altogether, say, three hundred nds, and, standing on one foot, rise to oe. Let us see what the strain on the tendo-Achillis is in doing so. Taking the distance from the fulcrum (2, Fig. 148) to the insertion of the tendon, 1, as one inch, and the distance from the same to the ball of the toes, J, as six inches, then we have the proportion 1, 2 = one inch : 2, j = 6 inches :: 300 pounds : x, and x — 1,800 pounds. Or if some one objects (as has been often. Fig. 148.—Diagram showing the power of the gastrocnemius and soleus muscles in Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York, D. Appleton and Company
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