HERMANN VON HELMHOLTZ 



not astonishing that physicists, as a rule, are shy of 

 dealing with physiological problems, and that they 

 regard many of them as practically insoluble. In the 

 judgment of the physicist, life, vitality, the mysteri- 

 ous something apparently unknowable, so interferes 

 with and obscures the play of the ordinary physical 

 forces, as to lead him to doubt whether the physical 

 phenomena of living matter can ever be thoroughly 

 understood. Now it is remarkable that, although 

 Helmholtz was already at the age of twenty-five a 

 great physicist, he boldly entered on physiological 

 research with the assured conviction that the play of 

 the physical forces in living matter was under the 

 same laws as in dead matter, and that the only way to 

 investigate, with success, the phenomena of living 

 matter, was to examine them by physical methods, and 

 to submit them, as far as possible, to physical analysis. 

 It was in this spirit that he began to investigate the 

 phenomena of animal heat, and this investigation led 

 him to lay the foundations of the great doctrine of the 

 conservation of energy. The subject occupied much 

 of his attention from 1844 to 1848, and he returned 

 to it in 1850, 1852, 1855 and 1859. The old view 

 that heat was a variety of imponderable matter had 

 been attacked long before by Voltaire, who, in a series 

 of elaborate experiments, endeavoured to prove that it 

 was only a kind of internal movement ; and in 1798 

 Count Rumford, one of the founders of the Royal 

 Institution, after executing a series of experiments on 

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