DIGESTIVE PROCESS. 119 



metamorphosis is accomplished in the stomach, acts 

 on the food. The insoluble matters become soluble 

 — they are digested. 



It is certainly remarkable, that hard-boiled white 

 of egg or fibrine, when rendered soluble by certain 

 liquids, by organic acids, or weak alkaline solutions, 

 retain all their properties except the solid form 

 (cohesion) without the slightest change. Their ele- 

 mentary molecules, without doubt, assume a new 

 arrangement ; they do not, however, separate into 

 two or more groups, but remain united together. 



The very same thing occurs in the digestive pro- 

 cess ; in the normal state, the food only undergoes 

 a change in its state of cohesion, becoming fluid 

 without any other change of properties. 



The greatest obstacle to forming a clear concep- 

 tion of the nature of the digestive process, which is 

 here reckoned among those chemical metamorphoses 

 which have been called fermentation and putrefac- 

 tion, consists in our involuntary recollection of the 

 phenomena which accompany the fermentation of 

 sugar and of animal substances (putrefaction), which 

 phenomena we naturally associate with any similar 

 change ; but there are numberless cases in which a 

 complete chemical metamorphosis of the elements 

 of a compound occurs without the smallest disen- 

 gagement of gas, and it is chiefly these which must 

 be borne in mind, if we would acquire a clear and 

 accurate idea of the chemical notion or conception 

 of the digestive ])rocess. 



