128 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



intestine. The consistence of the contents progressively in- 

 creases owing to continual absorption of the fluid portions, 

 until the pultaceous mass received by the cecum becomes 

 almost solid in the sigmoid. The degree of consistence may 

 be said to be greater the longer the sojourn in the large in- 

 testine. The proteids and carbohydrates which have es- 

 caped absorption in the small intestine are disposed of here, 

 partly by bacterial decomposition, and do not appear as such 

 in the feces. The absorption of easily digestible substances 

 in solutions, such as eggs, etc., from the lower bowel, al- 

 though there is no digestive enzyme there, is a matter of 

 common observation, but one which lacks explanation. 



Forms in Which the Different Classes Are Absorbed, i. 

 Water and Salts. Of course, water is absorbed in connec- 

 tion with all the foods as a vehicle for them, but water and 

 salts as such have been shown to be absorbed sparingly in 

 the stomach. They are soon conveyed to the small intestine, 

 where their rapid disappearance ensues. Hbwever, they 

 may be absorbed anywhere in the alimentary canal. The loss 

 of the water from the alimentary mass in the upper small in- 

 testine is compensated for by the secretions, so that the flu- 

 idity of the contents is not materially affected until the colon 

 is reached. Here absorption of water is active, and the 

 mass becomes more and more solid as the rectum is ap- 

 proached. 



2. Proteids. It is agreed that the first object of proteid 

 digestion is to render the nitrogenous foods more diffusible. 

 It is also agreed that the end products of such digestion, so 

 far as alimentary absorption is concerned, are proteoses and 

 peptones; and the natural conclusion, supported by experi- 

 mental evidence, is that these represent the forms in which 

 the proteids are absorbed. True, leucin, ty rosin, etc., fur- 

 ther end products of proteolysis, are formed, but these can 

 not be absorbed. The opinion that proteoses and peptones 

 are the absorbable forms of proteids is correct, for by far 

 the largest part of these foods are absorbed in this shape. 



