Chap, xii.] OF DIGESTION. 187 



We have seen that the albuminoidal vegetal substances are 

 generally contained in a membrane constituted by the cellulose ; 

 that is to say, that the vegetal aliments yield less easily than the 

 animal aliments their protei'c principles. In effect, the digestive 

 juices must fii-st of all dissolve more or less the refractory 

 envelopments. 



If we are -willing to depart from rigorous and literal strictness 

 in definitions, there is a laf ge amount of truth in the following 

 general formula of digestion — Stomachal digestion is histogene- 

 tical, that is to say, that it prepares the quaternary azotised 

 bodies destined to incorporate themselves with the anatomical 

 elements. On the contrary, but in a more general manner still, 

 intestinal digestion is thermogenetical ; it renders absorbable 

 principally the carburets of hydrogen, the ternary substances, 

 destined in great part to undergo in the economy a complete oxy- 

 dation, to be afterwards transformed into water and carbonic 

 acid in producing heat. 



Divers experiments of M. Schiff seem to prove that peptic 

 secretion does not depend on the central nervous system. After 

 the section of the pneumogastrie nerves the pepsine does not the 

 less continue to form itself in the glandular culs-de-sac, and the 

 stomachal absorption itself is not diminished.' The case seems 

 ■to be different in the acid secretion, and this explains how Wilson 

 Phillip, Brachet, Breschet, Milne-Edwards were able to see 

 digestion stop after the section of those same pneumogastrie 

 nerves. The first of these experimenters affirms even that he 

 succeeded in restablishing the digestive activity by galvanising 

 the peripheric trongon of the cut nerves. 



Besides, other experiments of M. Scheff show that the general 

 functions of the stomach are far from being independent of the 

 nervous centres. On dogs subjected to cerebral vivisections, to 

 lamisections of the optic layers and of the cerebral peduncles, 

 this physiologist demonstrated that the capillary vessels of the 

 stomachal mucous membrane dilated in places, that at those 

 1 M. Schiff, loc. ciL, p. 416. 



