RESORPTION OF PRODUCTS OF DIGESTION. 191 



As this disappears, it may be shown that the amount of material 

 which yields a crystalline precipitate with phosphotungstic acid 

 gradually increases, while the gelatinous precipitate, referable to 

 the albumoses, diminishes in amount and ultimately disappears. 

 Any coagulable albumins that may be present should be removed 

 before testing. 



Cohnheim's experiments thus place the observation that peptone 

 disappears from its solutions in the presence of pieces of intestinal 

 mucous membrane, in a new light. For it disappears, not because 

 the epithelial cells reconstruct albumins from this source, but be- 

 cause the erepsin causes its further cleavage to products which no 

 longer give the biuret reaction. Where and how the reconstruction 

 of the albuminous molecule then takes place is not known ; but 

 there can be no reasonable doubt that this occurs from the end- 

 products of proteolytic digestion, and that albuminous cleavage 

 and reconstruction thus go on in a manner perfectly analogous to 

 what we have already seen in the case of the carbohydrates. Some 

 observers believe that the reconstruction of the albuminous molecule 

 occurs in the intestinal mucosa and that the blood albumins, notably 

 serum-albumin, are here formed, and become the carriers of the 

 different radicles, from which the more highly differentiated albumins 

 in turn are built up in situ. Others maintain that the ultimate 

 cleavage-products are absorbed as such when they enter the portal 

 circulation and are reunited to form the albuminous molecule on 

 the distal side of the intestinal epithelial barrier. As a matter of 

 fact, Ho well has shown that such simple products actually occur in 

 the circulating blood. 



Of great interest in this connection are certain experiments of 

 Lowy, in which he succeeded in maintaining the nitrogenous equi- 

 librium of a dog by feeding with a mixture of the crystalline 

 decomposition-products, the result of pancreatic autolysis, in which 

 the biuret reaction could no longer be demonstrated. Abderhalden 

 and Rona obtained analogous results with hydrolyzed casein. 

 Henderson and Dean also performed similar experiments with 

 similar results, although they merely conclude that they established 

 a marked protein-sparing action on the part of the cleavage- 

 products. The hexon bases alone, as Ellinger has shown, are not 

 capable of maintaining nitrogenous equilibrium. 



The question whether or not native albumins can be absorbed as 

 such by the gastro-iutestinal mucosa can be answered in the affirma- 

 tive. A.scoli and Vigano have thus shown by the aid of the 

 precipitin reaction that native as well as deuaturized albumins can 

 pass the gastro-intestinal mucosa and enter the lymph and blood, 

 while retaining at least a portion of their biological characteristics. 

 To what extent this passage of native albumins occurs under normal 

 conditions remains to be seen. 



Whether or not albumoses can pass the intestinal mucosa with- 

 out undergoing further cleavage has not been satisfactorily ascer- 



