32 HERMANN VON HELMHOLTZ 



problem, in a paper published in Mutter's Archiv with the 

 title, ' Metabolism during Muscular Activity/ 



Lavoisier had already shown that a man who is doing work 

 requires more oxygen than a man at rest, but while it was 

 admitted that certain ponderable or imponderable substances 

 were consumed in the production of mechanical effects, and 

 were perpetually renewed by the vegetative vital processes, 

 and also that the amount of certain excreted nitrogenous 

 matters was increased by muscular activity, all data in regard 

 to the initial and intermediate steps of the process and the 

 seat of its occurrence were wanting. Helmholtz accordingly 

 set himself to investigate the modifications produced in 

 the chemical constitution of muscle by its own activity. 

 Resorting to the frog, 'that ancient martyr to science/ he 

 succeeded by means of the little electrical machine constructed 

 by himself, and of a Leyden jar, in showing that the compo- 

 nents within a muscle undergo chemical transformation during 

 its activity in virtue of the chemical processes described in his 

 account of fermentation and putrefaction ; and these conclu- 

 sions led him after protracted experiment to a series of 

 important results, which were for a long time the only exact 

 data in connexion with this subject. Yet, as he was per- 

 petually studying the inter-connexion of all these problems, 

 and their relation with the great law that governed his imagina- 

 tion, Helmholtz soon perceived that before he could obtain 

 exact data as to metabolism, it would be necessary to ascertain 

 the relations between muscular action and the heat therein 

 developed. This, however, entailed a fresh series of experi- 

 ments, which had to be left over for a later period. 



At Michaelmas he was to go up for the Government Examina- 

 tion at Berlin, and only had time before it to write an article 

 for the Encyclopaedia of Medical Science (issued by some 

 members of the Medical Faculty of Berlin), entitled ' Heat, 

 physiological/ which comprised the most recent observations 

 on animal heat. In this he strove to bring order into the 

 distorted conceptions then prevailing as to the nature of heat, 

 and the essay is distinguished by that grasp of the historical 

 development of the most heterogeneous branches of natural 

 science, for which Helmholtz was afterwards so generally 

 admired. 



