CHAP. XIL] OP DIGESTION. 191 



the digestive walls. The afflux of the biliary and pancreatic 

 liquids finishes and completes the chemical elaboration com- 

 menced in the superior portion of the digestive tube. The 

 amyloidal and saccharine substances are metamorphosed into 

 dextrine and glycose : the protei'c are transformed into peptones. 

 The fat bodies are emulsionised. 



All these important chemical modifications are effected, little 

 by little, 'in the degree that by the action of its muscular layer 

 the intestine contracts and thus makes the demi-liquid alimentary 

 mass march on. By degrees the aliments become assimilable 

 substances, veritable nutriments, Now these substances are in 

 contact in the intestine with the villosities so richly vascular : 

 they are therefore absorbed by endosmosis and thus pass into the 

 circulation. It is possible, however, that the vascular absorption 

 is not direct. There seems, in effect, to be incessantly on the 

 intestinal surface a generation of epithelial cells, which on the 

 one hand protect the mucous membrane, and on the other 

 absorb the nutritive liquids, elaborate them perhaps, then sur- 

 render them by endosmosis to the capillary vessels of the 

 intestine. 1 



The emulsionised fat bodies seem to be more specially seized 

 by the fine lymphatic canalicules, then to be driven thence into 

 the secondary lymphatic network. Therefore they give to this 

 network the milky aspect, fill it with chyle, which, drawn into 

 the grand lymphatic circulation, goes finally to pour itself into 

 the venous blood. 



The gastric biliary and pancreatic liquids are unquestionably 

 the principal chemical agents of the transformation of the 

 aliments : but they are not the only ones. Numerous small 

 glands of diverse forms are disseminated in the substance of 

 the intestinal mucous membrane. These glands secrete an 

 important digestive liquid, the intestinal juice, and also simple 

 mucus. It results from various experiments that the intestinal 

 juice is the auxiliary of the other digestive liquids already 

 1 Cl. Bernard, Rapport sur les Progrte de la Physiologic, etc. p. 199. 





