306 ABSORPTION 



But these experiments are not conclusive. If peptones are not to be found 

 under the circumstances named, it might be due to further decomposition, 

 and the discovery of erepsin makes such a view not improbable. The rapid 

 rise of the N-output in the urine after feeding proteid shows that it is de- 

 stroyed very soon after absorption. It would be a waste of energy if the body 

 were to construct native proteids out of albumoses and peptones, only to 

 destroy them immediately. The difficulty of obtaining a storage of proteid 

 in the adult body also can be easily harmonized with its ultimate cleavage 

 in digestion. 



Direct observations thus far at hand are not by any means sufficient to 

 establish a definite view of the matter. On the one hand, Cohnheim has found 

 that one-third of a cat's intestine surviving was able to split 0.6 g. of peptone 

 into its end products in two hours ; on the other hand, Glaessner finds that albu- 

 moses are changed by the surviving mucous membrane into coagulable com- 

 pounds ; whereas Emden and Knoop reach the conclusion that in the surviving 

 intestine taken while absorption of proteid was going on, there is neither a 

 reconstruction of coagulable proteid out of albumoses and peptones, nor a cleav- 

 age of them into final products. They as well as Langstein state that from all 

 appearances albumoses occur plentifully in the blood. 



So far as the question can be judged at present, we might say that a part 

 of the proteid eaten is absorbed as end products of digestion, another part as 

 albumoses and peptones. How and where the latter are transformed into 

 native proteids, and whether a synthesis of proteid from the end products 

 can take place under any circumstances,, cannot yet be decided. 



Our knowledge is still unsatisfactory also with regard to the manner of 

 the absorption of proteids. Hofmeister has supposed that the leucocytes of 

 the mucous membrane are especially active in this, and the following facts 

 among others appear to favor such an hypothesis. After meat feeding the 

 lymph system in the small intestine of rats exhibits a larger number of cellu- 

 lar elements than after feeding lard or starch, but with the latter, more than 

 in fasting (Asher). An hour after a meal rich in proteid, the number of 

 leucocytes in the portal blood of the dog is considerably increased, and reaches 

 a maximum probably during the third hour of digestion. This increase does 

 not occur if the animal receives water, meat extract, salt, starch or fat, but 

 no proteid. In proteid absorption, finally, the number of leucocytes in the 

 venous blood of the intestine is greater than in the arterial blood (Pohl). 



Some have sought to demonstrate an increase in the number of leucocytes 

 in the skin capillaries of man after a meal rich in proteids ; but this digestive 

 leucocytosis is often wanting and is entirely denied by some authors. The 

 possibility remains, however, that the leucocytes may take part in the absorp- 

 tion of proteids ; for it is easily conceivable that the transportation of proteids 

 from the intestine might be assisted by them, without their entering the 

 general circulation in larger numbers, 



The pathway which the proteids take in leaving the intestine is almost 

 exclusively that of the portal vessels. In the fistulous patient above-mentioned 

 (page 303) it was impossible after a meal rich in proteid to demonstrate any 

 increase in the percentage of proteid in the chyle. 



