ABSORPTION 4 2 T 



with the power of absorbing (and perhaps transforming) these 

 substances, but the balance of evidence is in favour of the 

 epithelial cells. We cannot, however, as in the case of the fat, 

 single out any particular tract of epithelium as alone engaged in 

 the absorption (and possibly in the resynthesis) of the products 

 of the digestion of the protein?. In all likelihood the cells covering 

 the villi are actively concerned, but there is no valid reason for 

 denying a share to the general lining of the stomach and small 

 intestine, even including the Lieberkiihn's crypts, which morpho- 

 logically form a kind of inverted villi. It is, indeed, true that 

 the crypts do not take part in the absorption of fat, for no 

 granules blackened by osmic acid occur in them during digestion 

 of a fatty meal. But this is a ground for attributing to them 

 other absorptive functions rather than for altogether denying 

 to them a share in absorption, unless, indeed, we assume that 

 the secretion of the succus entericus engrosses the whole activity 

 of this extensive sheet of cells. 



The extraordinary efficiency of the small intestine in digestion 

 and absorption is shown by the fact that after removal of even 

 70 to 83 per cent, of the combined jejunum and ileum in dogs, 

 the metabolism is not necessarily much affected. On a diet 

 poor in fat the animals absorb as much of the fat as a normal 

 dog, although a smaller proportion when the diet is rich in fat. 

 It has been generally stated that it is never permissible to 

 remove more than one-third of the small intestine in man. But 

 in one case 2| metres was resected, or quite one-half, and the 

 patient recovered. Even the large intestine, which possesses 

 Lieberkiihn's crypts, but no villi, is able to absorb not only 

 peptones and sugar, especially monosaccharides like dextrose, 

 but also fats and undigested native proteins. And, although 

 these are powers which can be rarely exercised to any great 

 extent in normal digestion, they form the physiological basis 

 of the important method of treatment by nutrient enemata. 

 The observation already mentioned (p. 309), that considerable 

 quantities of food administered by the rectum can pass through 

 the ileo-colic sphincter and valve into the lower part of the 

 ileum, thanks to the antiperistaltic movements of the large 

 intestine, indicates that an important part of the preliminary 

 digestion and of the absorption of enemata may occur in the 

 small intestine. But remnants of the proteolytic, amylolytic, 

 fat-splitting, and inverting ferments which have done their work 

 in the small intestine are passed on into the large, and may be 

 demonstrated in its contents. Doubtless these are able to 

 act upon food substances which may have escaped complete 

 digestion and absorption in the higher parts of the alimentary 

 canal, as well as upon food substances injected into the rectum. 



