CHAP, vi.] OF DIS- ASSIMILATION AMONGST ANIMALS. 139 



Oxygen is certainly the determinating agent in the composition 

 of all these regressive bodies. Nevertheless, according to 

 M. Robin, there is not here simple oxydation, but oxydation 

 with evolution, and often simple evolvent catalysis, in technical 

 terms. It would even be necessary, in relation to this, to 

 establish a kind of antagonism between assimilation and dis- 

 assimilation. The one would operate through metamorphic 

 catalysis, and the other through evolvent catalysis. These are 

 data which can only be admitted with considerable reservation. 

 In fact we can, in a certain degree, note in passing the substances 

 which enter into an animal organism, and those which issue from 

 it ; but, from the ingress to the egress, a succession of reactions 

 and transformations has taken place, which we are far from 

 having traced step by step, since we have not yet even succeeded 

 in giving the definitive formula of the albuminoTdal substances. 



