v INTEENAL EESTITUTIVE SECEETIONS 269 



end of the ileum described by Braun and Ewald, on the contrary, 

 the body-weight was tolerably well maintained on an abundant 

 diet per os, notwithstanding the considerable loss of nutritive 

 substances through the fistula. 



The maximal degree of absorption of the food-stuffs from 

 the chyme is effected principally in the duodenum (below the 

 orifices of Wirsung's duct and the common bile duct) and the 

 jejunum. Euggi's case of extensive resection of the ileum referred 

 to in the last chapter (iv. 5), in which the faeces did not contain 

 an abnormal excess of proteins, fats, and carbohydrates, is a direct 

 proof that, owing to physiological adaptation, nearly the whole of 

 the intestinal absorption can be performed in the upper part of 

 the small intestine. 



Normally, therefore, no absorption of food-stuffs worth noting 

 takes place in the large intestine. The absence of villi (see Fig. 

 42, p. 123) and of valvulae couniventes, and the superabundance of 

 mucin-secreting crypts, support this conclusion. A physiological 

 argument for the insignificant absorption of food -stuffs which 

 takes place under normal conditions in the large intestine, is 

 shown by the fact that in no -cases of fistula of this part of the 

 gut, as described for man, was any diminution of weight observed 

 in the individuals affected (Czerny, Marckwald). In dogs, on the 

 contrary, according to Albertoni, nutritive absorption is not com- 

 pleted in the small intestine, but continues in the large bowel. 

 These animals, in fact, become emaciated with a fistula of the 

 caecum. Harley's recent researches confirm these observations, 

 and show that dogs with fistula of the large bowel absorb fats and 

 carbohydrates normally, but proteins only imperfectly. 



Hardly anything but water is normally absorbed in the large 

 bowel of man. It is, in fact, in this part of the gut that the 

 intestinal contents assume the pasty consistency proper to faecal 

 matter, and the mucin secreted by the crypts of the large intestine 

 (supra] lubricates the surface of the faeces, and facilitates their 

 expulsion. 



Later on we shall see how under abnormal conditions of 

 alimentation per rectum the large bowel is capable of absorbing 

 not only diffusible substances such as alcohol, salts and glucose, 

 but also colloidal substances, including protein. 



III. Before we attack the study of the complex mechanism of 

 intestinal absorption, it will be advisable to obtain some idea of 

 the paths which the food-stuffs take after absorption, this question 

 being simpler and easier of solution, so that it leads up to the other. 



From the time of Bartholin, who completed the discoveries of 

 Aselli, Pecquet, and Eudbeck on the so-called Vasa Lactea, until a 

 few years ago, there was a tendency to assume that the principal 

 stream of food-stuffs from the intestine to the blood was repre- 

 sented by the chyle flowing through the thoracic duct. The work 



