62 PROTEIN DIGESTION IN THE INTESTINE 



Interesting as such observations in themselves may be, 

 the greatest caution should be observed in interpreting their 

 physiological significance. That the physico-chemical rela- 

 tions in as complicated colloid system as blood serum on the 

 addition of a second, no less complex system, like Witte's 

 peptone, may be decidedly disturbed is in nowise surprising. 

 It is very questionable whether any sort of conclusion is 

 justifiable from such static change as to the actual physiology 

 of absorption. 



Par entered Introduction of Protein. E. Freund 44 is of 

 the opinion that the very fact of elaboration of parenterally 

 introduced albumoses by the tissues, etc., bespeaks collabor- 

 ation of the intestine. "Five minutes after intravenous 

 injection of Witte's peptone, renal elimination being pre- 

 vented, only about half the injected substance remains in the 

 blood. The fate of the peptone remaining in the blood appar- 

 ently depends upon whether or not the intestinal blood ves- 

 sels be traversed or not. If these are closed off the great 

 bulk of the injected incoagulable substance remains in the 

 blood . . . " Other experiments, 45 as those conducted by 

 von Korosy, upon the fate of parenterally introduced pro- 

 teins in conditions of intestinal exclusion are, however, not 

 confirmatory of Freund 's assertion; according to these all 

 protein to undergo cleavage in the organism must first pass 

 the intestine and there undergo a particular preparation. 



Eeturning to the major question, as to the ability of the 

 intestine to dissociate protein to its elementary building- 

 stones: there can no longer be the least doubt of this if 

 Abderhalden's investigations are to be accepted. 46 The 

 older view that proteid nitrogen is absorbed exclusively in 

 the form of " albumoses" and "peptones" is no longer ten- 

 able in the light of this knowledge. Another question, how- 



44 E. Freund and H. Popper, Biochem. Zeitschr., 15, 272, 1909; G. Topfer, 

 Zeitschr. f. experimental Pathol., 3, 45, 1906; E. Freund and G. Topfer, ibid., 

 3, 633, 1906; E. Freund, ibid., 4, 1, 1907. 



45 K. v. Korosy (Budapesth), Zeitschr. f. physiol. Chem., 62, 68, 1909. 



46 Cf. E. Abderhalden, Zeitschr. f. physiol. Chem., 74, 436, 1911. 



