5 o HERMANN VON HELMHOLTZ 



did more than Mayer, and that many particulars are confused 

 in Mayer's first note, we must, I think, regard him as a man 

 who of and for himself conceived the idea which has rendered 

 the great recent advance of natural science pqssible, nor is 

 his merit in any way lessened by the fact that another man, 

 in another country and different sphere of activity, had 

 simultaneously made the same discovery, and worked it out 

 afterwards with greater completeness.' 



Robert Mayer himself was far from claiming priority over 

 Helmholtz in his epoch-making work, and the Naturforscher- 

 Versammlung at Innsbruck in 1868, at which Helmholtz ac- 

 knowledged Mayer's priority clearly and without ambiguity 

 wherever it was due, left the two distinguished men on the 

 best possible understanding. 



With this work on the Conservation of Energy, Helmholtz 

 took first rank not only among physicists, but among physiolo- 

 gists also, who recognized that his law afforded them an 

 invaluable weapon for the attack upon vitalism; and he now 

 went on to verify it for the natural processes of living 

 organisms, by continuing his earlier experiments on the de- 

 velopment of heat during muscular activity. His results were 

 given to the Physical Society in November, 1847, and published 

 the next year in M tiller's Archiv. 



This research, which is a model of the application of the most 

 delicate physical methods to physiological problems, was in- 

 tended to determine whether the rise of temperature in a working 

 muscle takes place in the substance of the muscle itself, in conse- 

 quence of internal processes brought about during contraction 

 by a disturbance of equilibrium, or whether it is merely the 

 result of increased flow of arterial blood. While the previous 

 thermo-electric determinations of temperature in animals had 

 been made with only a Becquerel couple, Helmholtz employed 

 a triple junction of iron and German-silver which trebled the 

 electromotive force, and found with the finest measurements, 

 and ingenious contrivances for the exclusion of every other 

 increase of temperature, that in excised and isolated thighs 

 of the frog, there was a rise of temperature derived solely 

 from molecular processes, when the muscle was caused to 

 contract by stimulating the spinal cord with a Neefs inter- 

 rupter modified for the purpose. The heat in contraction was 



