374 A MANUAL OF PHYSIOLOGY 



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 morphologically 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, especially as it seems unlikely that the secre- 

 tion of the comparatively scanty and relatively unimportant 

 succus entericus should engross the whole activity of such 

 an extensive sheet of cells. Even the large intestine, which 

 possesses Lieberkiihn's crypts but no villi, is able to absorb 

 not only peptones and sugar, but also undigested proteids ; 

 and although these are powers which can be rarely exercised 

 in normal digestion, they form the physiological basis of the 

 important method of treatment by nutrient enemata. 



We may add to the proof of the varied powers of the cells 

 of the intestinal wall given by the change which proteoses 

 and peptones undergo in their passage through them the 

 facts, already mentioned, that cane-sugar does not pass into 

 the blood as such unless large quantities are given, but is 

 first converted into dextrose, even in the absence of an 

 inverting ferment, and the remarkable discovery of Munk, 

 that fatty acids given by the mouth appear in the lymph of 

 the thoracic duct as neutral fats, having somewhere or other, 

 in all probability on their way through the epithelium of the 

 gut, been combined with glycerine. 



Since, however, the amount of neutral fat recovered from 

 the thoracic duct is not equivalent to more than one-third 

 of the fatty acids given, it has been suggested that this 

 synthesis of fat is only apparent, and that the whole of the 

 fat which appears in the chyle after a meal of fatty acids 

 comes from the fat excreted into the intestine (Frank), 

 which is increased when fatty acids are given by the mouth. 

 But the suggestion is more ingenious than the evidence 

 advanced in its support is convincing. 



