312 AN AMERICAN TEXT- BOOK OF PHYSIOLOGY. 



the portal circulation, before they reach the general circulation. During this 

 passage through the liver, as we shall find, changes of the greatest importance 

 take place. The physiology of absorption is concerned with the physical and 

 chemical means by which the end-products of digestion are taken up bv the 

 blood or the lymph, and the relative importance of the stomach, the small 

 intestine, and the large intestine in this process. Leaving aside the fats, 

 whose absorption is a special case, the absorption of the other products of 

 digestion was formerly thought to be a simple physical process. The processes 

 of diffusion and osmosis, as they are known to occur outside the body, were 

 supposed to account for the absorption of all the soluble products. This 

 belief is still held by many, hut the facts known with regard to the absorp- 

 tion of the carbohydrates, proteids, and fats after the changes undergone 

 during digestion are not wholly accounted for by the laws of diffusion and 

 osmosis as they are known to us (see p. 65 for a discussion of the nature of 

 these processes). For the present at least it seems to be necessary to refer 

 many of the phenomena of physiological absorption to the peculiar properties 

 of the living epithelial cells lining the alimentary canal. Some of the 

 important facts regarding absorption are as follows : 



Absorption in the Stomach. — In the stomach it is possible that there 

 might be absorption of the following substances : water; salts; sugars and 

 dextrins that may have been formed in salivary digestion from starch, or 

 that may have been eaten as such ; the proteoses and peptones formed in 

 the peptic digestion of proteids or albuminoids. In addition, absorption of 

 soluble or liquid substances — drugs, alcohol, etc. — that have been swallowed 

 may occur. It was formerly assumed without definite proof that the absorp- 

 tion in the stomach of such things as water, salts, sugars, and peptones was 

 very important. Of late years a number of actual experiments have been 

 made, under conditions as nearly normal as possible, to determine the extent 

 of absorption in this organ. These experiments have given unexpected results, 

 showing, upon the whole, that absorption does not take place readily in the 

 stomach — certainly nothing like so easily as in the intestine. The methods 

 made use of in these experiments have varied, but the most interesting results 

 have been obtained by establishing a fistula of the duodenum just beyond the 

 pylorus. 1 Through a fistula in this position substances cau be introduced into 

 the stomach, and if the cardiac orifice is at the same time shut off by a ligature 

 or a small balloon, they can be kept in the stomach a given time, then be 

 removed, and the changes, if any, be noted. After establishing the fistula in 

 the duodenum food may be given to the animal, and the contents of the 

 stomach as they pass out through the fistula may be caught and examined. 

 The older methods of introducing the substance to be observed into the 

 stomach through the oesophagus or through a gastric fistula were of little use, 

 since, if the substance disappeared, there was no way of deciding whether it 

 was absorbed or was -imply passed on into the intestine. 



1 ( lompare von Mering: Verhandl. </<:< Congresses f. innere Med., 12, 471, 189.'?; Edkins: 

 Journal of Physiology, 1892, vol. 13, p. 44".; Brandl: Zeii&chrift fur Biologie, 1892, Bd. 29, 

 8. 277. 



