DIGESTION OF THE ALBUMINS. 179 



Aside from its proteid character, casein differs from the common 

 albumins in one very important particular, namely, in the exceed- 

 ingly small number of hexon groups which the substance apparently 

 contains. In its an ti peptone, therefore, which has not as yet been 

 studied in this direction, however, we can hence not expect these 

 bodies beyond traces. 



The glucoproteids and the hemoglobins are decomposed as in the 

 case of the gastric juice, and the albuminous components further 

 digested like the native albumins. The individual products, how- 

 ever, which are thus formed have not as yet been studied in detail. 



The true nucleins, which, as we have seen, escape gastric diges- 

 tion and which do not undergo solution in the stomach, are dissolved 

 by the pancreatic juice and are decomposed with the liberation of 

 the contained nucleinic acids and the albuminous radicles. The 

 latter are further digested in the usual manner. The paranucleins 

 similarly undergo dissolution, and are probably decomposed as 

 already indicated. Of the subsequent fate of the non-albuminous 

 pairlings of the proteids in general, however, but little is known. 



Digestion of the Albuminoids. 



The only albuminoids which are digested in the stomach in the 

 case of the higher vertebrate animals are collagen and elastin. 

 Both then give rise to protogelatose and proto-elastose, respectively, 

 while curiously enough hetero-albumoses are not formed. The cor- 

 responding detitero-albumoses then result. But while the deutero- 

 gelatose subsequently gives rise to the formation of peptone the 

 so-called glutin-peptone a similar transformation of the deutero- 

 elastose apparently does not occur. 



In the small intestine, under the influence of the pancreatic 

 juice, collagen and elastin can also be digested, and it is note- 

 worthy that the transformation of the gelatins into glutin-peptone 

 is apparently more readily effected than that of any other albumin- 

 ous substance. Unlike the gastric juice, however, the pancreatic 

 secretion is in itself not capable of transforming the native collagen 

 into gelatin. This change must hence be first effected artificially 

 or in the stomach before its further digestion can occur. The 

 peptonization of elastin in the pancreatic juice likewise ceases with 

 the formation of deutero-elastose, while gelatin is transformed in 

 vitro, at least, into glutin-peptone. According to Chittenden, this 

 is not further decomposed by the trypsin, and amido-acids are hence 

 not formed. This is rather remarkable, as on hydrolytic decom- 

 position with mineral acids gelatin yields leucin, asparaginic acid, 

 glutaminic acid, and considerable amounts of glycocoll. The existence 

 of aromatic groups in the original molecule, on the other hand, is 

 very doubtful, and as a matter of fact it is impossible to obtain 

 either tyrosin, or indol, or skatol, from the substance, even on bac- 

 terial decomposition. Hexon groups, however, are largely present. 



