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Before proceeding to apply this principle of least action or least 

 trouble to nature, it is necessary for us to obtain what I call the co- 

 efficient of muscular force. If you take a rope made of hemp, of silk, 

 or of iron, engineers are well-acquainted with the importance of obtain- 

 ing its coefficient, which represents the number of pounds or tons 

 weight necessary to break it across. Now, I ask you to imagine a rope 

 of muscle. A muscle consists of filaments or fibres very frequently 

 parallel to each other in the form of a rope. Imagine a rope of muscle, 

 dne square inch in cross-section, hanging from the ceiling to the 

 ground : let that muscle contract by the order of the will, what weight 

 will it lift from the ground ? This is what I define as the coefficient of 

 muscular contraction. It has cost me twelve years of hard work to 

 obtain the coefficients I now place before you, which are represented 

 in pounds per square inch for human muscle. I have not succeeded in 

 obtaining it for any other animal but man. No other animal that I 

 have met with, not even the " hairy quadrupeds with long tails", are 

 intelligent enough to submit to the necessary experiments. 94. 7 lbs. per 

 square inch is the weight that the arms of a young man accustomed to 

 athletic exercise are capable of lifting, no. 4 is the corresponding co- 

 efficient for the muscles of the legs of a similar class ; and 107 for the 

 muscles covering the abdomen. 



When you bear in mind what I shall now call your attention to, the 

 extreme difficulty of obtaining these results at all, I hope you will 

 agree with me that the differences between them fall within the neces- 

 sary limits of observation and of error, and that therefore the final re- 

 sult of 104 per square inch may be regarded as an extremely close ap- 

 proximation to the real coefficient of muscular force exerted in healthy 

 strong men. At least, it is the only coefficient that I am able to lay 

 before you. We must undertake, and I did undertake, two extremely 

 laborious classes of observations in order to obtain that coefficient. 

 Without that coefficient I can make no step further in the application 

 of geometry and mechanics to anatomy. This became an absolutely 

 necessary preliminary step. The determining of that coefficient re- 

 quires two totally distinct classes of observations. I had to make ob- 

 servations on the force exerted by the muscles during life ; and, 

 secondly, I had to make most careful measurements after death of 

 those same muscles. With regard to observations on the force of the 

 muscles exerted during life, it is not nearly so easy to make them, as 

 many of you, who are not anatomists, would at first sight suppose. 

 There is hardly an action of the body — the lifting my hand to my 

 head, walking across a room — that does not involve the co-ordination 

 and co-operation of many scores of muscles ; and the moment I get 

 many muscles into play, the difficulty of separating their action becomes 

 immense. Although it is easy to measure the force used in rowing and 



