218 JOHN C. KOCH 



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could be readily calculiited from the principles of mechanics. 

 A comparison of the stresses produced by the dead load with 

 the strength of each part of the structure would show in prac- 

 tically every case a fairly close agreement, or parallelism, which 

 would be conclusive that the parts were proportioned in accord- 

 ance with mathematical laws. Further study of the design 

 would show the amount of moving load, etc., that could be safely 

 applied to the structure. 



In the femur the body weight in the standing, walking or 

 running positions produces preponderant stresses, which are 

 much greater in magnitude than normally may be produced by 

 the muscles alone. For example, in walking it will be shown 

 that the maximum stress in the neck of the femur is 2098 pounds 

 per square inch and in running it is 4192 pounds per square 

 inch in the specimens analyzed in this paper. As the ultimate 

 strength of muscle is about 77 pounds per square inch and it 

 has practically no compressive strength, it is evident that the 

 role of the muscle as affecting the inner architecture of the 

 femur must be secondary to that of the static loads transmitted 

 through the femur-head due to the superincumbent body weight. 

 As the mechanical effects produced by the body weight acting 

 through the femur-head are undoubtedly far greater than those 

 normally due to muscle action, the structure of the femur must 

 be designed to resist these maximum stresses due to body 

 weight. 



For these reasons, in this study no attempt will be made to 

 analyze the effect of various muscles, or combinations of muscles, 

 as affecting the inner architecture. A more detailed discussion 

 of such effects is given in a subsequent paragraph (p. 224). 



The mechanism of human locomotion 



The modern views of this subject began with the publication of 

 Borelli's classic (1681). Little further progress in the study of 

 human locomotion was accomplished until the appearance of the 

 epoch-making work, Die Mechanik der menschlichen Gewerk- 

 zeuge, by the Weber brothers in 1836. Their ingenious and 



