LARGE INTESTINE. 275 



tion as produced by the difference in the specific heat of 

 those fluids which surround the membrane to be traversed : 

 he looks upon the osmosis which then takes place as a 

 physico-chemical property, in virtue of which the miscible 

 fluids have a tendency to mix in the membrane, one current 

 predominating over another. All other things being equal, 

 the direction and intensity of the current are determined by 

 the differences in specific heat. The figures given by J. 

 Beclard, in support of this theory, showing the specific heat 

 of the different fluids, agree perfectly with what we know of 

 their flowing towards each other. However plausible this 

 theory may appear, it is only a physical theory of osmosis / 

 and knowing, as we do, the important function of the living 

 cell, we cannot imagine that, in the phenomenon of intestinal 

 absorption, it simply plays the part of an inert membrane. 



V. LARGE INTESTINE. 



THE aliments that pass out from the stomach form a 

 fluid mass ; we have seen that they become still more fluid 

 by the addition of the pancreatic and enteric juices. How- 

 ever, as these matters pass through the small intestine, their 

 consistency increases, while their bulk diminishes, the greater 

 part being absorbed. The small intestine, therefore, delivers 

 to the large inte-stine only a solid substance, or waste, which 

 is to be thrown off, and is prevented from passing back again 

 by the ileo-ccecal valve, which renders any reflux impossible. 

 In man, very little digestive action takes place in the large 

 intestine ;' the small amount which has escaped absorption 

 are here, however, drawn into the blood current, and the 

 large intestine may even absorb fluids directly introduced 

 into it. After injection, by the rectum, of fatty substances 

 (fats in a state of emulsion), the lymphatic vessels leading 

 from the large intestine exhibit the same features, the same 

 chyliferous appearance, as those of the small intestine. The 

 villi are not found here, but their place is supplied by nu- 

 merous folds in the mucous membrane. In herbivorous ani- 

 mals, whose caecum is very much developed, this part of the 

 intestinal tube is the seat of actual digestive phenomena : 

 the cfficum may therefore be considered as a sort of second 

 stomach ; it contains acids which suffice for the digestion of 

 the vegetable albuminoids. It is not certain that these 

 acids are secreted from its walls: they are, more probably, 

 produced by the aliments themselves. They increase in 



