Origin of Muscular Power. 487 



The doctrine that muscular force is produced only by the oxi- 

 dation of albuminoid compounds, is, however, much more seri- 

 ously shaken by the important investigations of Edward Smith, 

 who has shown, in the most convincing manner, that the produc- 

 tion of carbonic acid in the human body may be increased ten- 

 fold by muscular exertion, whilst the excretion of urea proceeds 

 with tolerable uniformity. The latter fact has also been fre- 

 quently observed by other inquirers, viz. by Bischoff and Voit 

 (in part before the investigations of E. Smith). The numbers 

 given by Smith do not, however, furnish quite a direct disproof 

 of the doctrine in question. If any adherent of that doc- 

 trine felt inclined to retain it on any terms, he might reply to 

 Smith, " Probably muscular action necessarily excites the pro- 

 cess of oxidation of non-nitrogenous substances without these 

 compounds having anything to do with the production of that 

 action." On the other hand, the objection might be made to 

 Smith, that perhaps, when there is violent exertion of the mus- 

 cles, though the metamorphosis of compounds containing nitro- 

 gen is increased, yet the secretion of urea is not larger, because 

 the results of the metamorphosis of these compounds leave the 

 body in other forms. 



There is one way in which the question whether muscular 

 force can be generated only by the oxidation of albuminoid com- 

 pounds might be decisively negatived, and that possibly by a 

 single experiment. It is suggested by the following simple 

 line of thought. Granting that a person might accomplish a 

 certain measurable amount of external labour, say m metre-ki- 

 logrammes, and that in so accomplishing it he oxidizedj9 grammes 

 of albumen in his muscles; granting also that we know the 

 amount of heat which is liberated when a gramme of albumen 

 is changed by oxidation into the products of decomposition in 

 which the constituents of albumen leave the human body ; then 

 if the thermic equivalent of the manual labour m be greater than 

 the amount of heat which could possibly be produced by the 

 oxidation of p grammes of albumen, the question may be nega- 

 tived with the most complete certainty. But if, on the contrary, 

 the thermic equivalent of m metre-kilogrammes is less than that 

 of the heat arising from the oxidation of p grammes of albumen, 

 the question has by no means received an affirmative answer. 

 It is only in the former case that the experiment has a decisive 

 result. 



Such an experiment has been made by us conjointly. It is 

 true that the quantities which require to be determined, with 

 the exception of the mechanical work, cannot have any exact 

 numerical value assigned to them ; but we can confine their 

 values within certain limits, so that a satisfactory conclusion 



2K2 



