CARBONIC ACID THE PRODUCT OF DISINTEGRATION. 489 



the voluntary muscles are unceasingly in action ; but it is in 

 the exercise of greater or less bodily activity that the disin- 

 tegration of the voluntary muscles principally occurs. To 

 confine our attention, then, to the muscular system, this disin- 

 tegration, which is continually going on, is manifested princi- 

 pally in the production of carbonic acid the effect being, that 



system require, is undeniable ; yet it seems, prima facie, so pro- 

 bable that the muscular system itself affords the material by the 

 oxidation of which mechanical energy is generated, that the im- 

 possibility of such being the case almost requires proof before 

 Franklaud's idea of the blood being its source finds any room to 

 be entertained. 



But to clear the way towards the exact point under dispute, it 

 should be premised that there is a general agreement among the 

 partisans of the doctrine of the "conservation of energy " that the 

 amount of carbonic acid produced in a living body within a given 

 period is an index of the whole energy expended in that interval 

 on the several kinds of work performed therein namely, heat 

 work, vital work, nerve work, and external mechanical work. 

 And now to come to the point in dispute ; what is affirmed by one 

 party namely, that muscular energy is the effect of disintegration 

 of the muscular substance by its conversion into carbonic acid and 

 azotised compounds, commonly thrown off by the kidney is 

 denied by the other party, on the ground of the urea and allied 

 compounds in. the urine not being uniformly in corresponding 

 measure with the muscular exertion performed in the period of 

 which note has been taken. 



Such statements as the following are strongly in favour of the 

 belief in respect to muscular disintegration being the source of me- 

 chanical energy in living bodies. Non-nitrogenised alimentary sub- 

 stances, such as starch, sugar, oil, hardly maintain life beyond the 

 period to which it is prolonged under complete abstinence, while, on 

 inspection after death, all the usual marks of death by starvation 

 are met with. On the other hand, when death occurs in an animal 

 confined to one azotised nutritive principle, life is prolonged be- 

 yond the period required for death by starvation, and the appear- 



