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XIY. 



HTJMA:N" LOCOMOTIO^T: YAEIATIOX of TELOCITY WHEN 

 WALKIXG. By EALPH CUSACK. 



(Plate Y1.) 



(COlEMimrCATED BY G. FITZGERALD, D.SC, F.T.CD.) 

 (Bead April 26, 1897.) 



OxE remarkable provision of nature often overlooked is the ease and 

 smoothness with which man walks, especially when it is con- 

 sidered that the impulse forward is received only about once in 

 the second. Dr. Joly first called my attention to these facts and 

 pointed out that when a man was seen walking across a Yenetian 

 blind, which shut ofE his up and down motion, his walk appeared 

 to be very uniform. Observe a boy walking on stilts, his motion 

 always appears jerky, his legs are kept quite stifE, and the elasticity 

 of the muscles of his legs and feet cannot come into play, which 

 they do when he is walking naturally along the ground. 



The following experiments will show to some extent the degree 

 of uniformity with which an ordinary man walks and how the 

 uniformity varies with circumstances in the same individual : — 



The greatest difficulty in obtaining the variation of velocity of a 

 man walking is to record the velocity without the individual being 

 conscious of it. If the individual knows that he is walking for a 

 certain purpose, the velocities recorded are not that of the uncon- 

 scious mechanical walk, but that of the voluntary. Thus the question 

 arises, in what way do these two walks differ, if they differ at all ? 

 That they differ, and that the mechanical walk is more imiform than 

 tlie voluntary appears obvious, inasmuch as all our mechanical move- 

 ments are more regular than our voluntary movements. As an 

 example, when the number of respirations of an individual are being 

 measured, so long as the person's attention is distracted from the 

 apparatus, the record of his breathing is unifonn, but if his attention 

 is called to the fact that his respirations are being recorded, the 



