648 



ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1911. 



had achieved that object he had broken down, at any rate, temporarily. It was well 

 known that in a 100-yards race the man who made the greatest effort, and put the 

 greatest possible endurance into that effort, was practically absolutely exhausted, and 

 this corresponded to the yielding of the metal specimen when it gave way. It was the 

 same with the man who ran 100 miles, but he could only maintain a less speed for that 

 distance; the same result was obtained with the breaking down of the metal under less 

 stress when the reversal of stress was further prolonged, and there was every reason for 

 both kinds of curves being logarithmic in form as they were. Thus, muscular fatigue 

 corresponded in a certain way to the endurance tests of metals. 



It was only quite recently that physiologists had understood the reason of the limita 

 of muscular endurance, which limit was reached because of the formation of the toxins 



100 



MILES 



Fig. 7.— Fatigue curve of metals, compared with muscular fatigue, fig. 2. 



in the muscles, and which toxins must be dissipated and the muscle renewed. Thus, 

 if a man made a certain effort, he could not renew the toxins sufficiently quickly to keep 

 that effort going beyond a certain distance. In the case of metals was there anything 

 similar comparable with that? In that connection he approached a subject that had 

 already been alluded to by previous speakers, though not in such a way as to account 

 for the results he had referred to. Scientists at the present time, did, however, know 

 the reason, and had discovered an explanation of the extraordinarily puzzling phe- 

 nomenon of fatigue of metals as well as of muscular fatigue. He had before him a proof 

 copy of the most valuable and interesting lectures 1 that Dr. Rosenhain delivered 



> Proceedings 1911, pt. 2, p. 241. 



