SUMMARY 73 



normal conditions the cleavage of protein by digestion in 

 the gastro-intestinal canal ultimately extends to the stage of 

 aminoacids." 69 We lose track, practically under our very 

 eyes, of the split products of the protein molecule as they 

 pass out from the intestine into the blood. Accumulation 

 of albumoses or of aminoacids in the blood of an individual 

 in the course of digestion under entirely normal and physio- 

 logical conditions has not been established beyond doubt, and 

 on the other hand has not been definitely disproved. There 

 is some justification therefore in the suspicion that there 

 occurs a protein reconstruction in the wall of the 'intestine. 

 The author believes, too, that it is by no means improbable 

 that both the smaller and the larger cleavage products of the 

 protein molecule may enter the circulation, be carried to the 

 various organs and in the latter be further elaborated ac- 

 cording to the local requirements, either being condensed 

 into new protein molecules, or in further dissociation finally 

 passing into various end-products (ammonia, carbon 

 dioxide and water) . 



The biological serum reactions (precipitin-reactions,etc.) 

 have led to an appreciation of the almost endless multiplicity 

 and specific peculiarities of the proteid substances with 

 which nature deals. Axiomatically we come to the assump- 

 tion, from the fact that every individual contains in the 

 various fluids and tissues an enormous number of chemically 

 variant proteid substances, that doubtless no two different 

 kinds of animals contain exactly identical proteins. 



This tremendous multiplicity may be appreciated if we 

 think of the equally tremendous number of variations in 

 which the great numbers of ^ mosaic stones" of the protein 

 molecule may enter into combination in its construction. 

 That a given individual, no matter the extreme variety of 

 proteids entering into its food, is capable, always and under 



68 E. Abderhalden, Synthese der Zellbausteine in Pflanze und Tier, pp. 53 

 and 71, Berlin, J. Springer, 1912; cf. Zeitschr. f. physiol. Chem., 78, 382, 1912. 



