188 THE PROCESSES OF DIGESTION AND RESOUPTION. 



Caseoses then result as with the common native albumins, and finally 

 peptones are formed. 



The glucoproteids and the haemoglobins 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 give rise to protogelatose and proto-elastose respectively, while 

 hetero-albumoses are not formed. The corresponding deutero- 

 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, a,t least, into glutin-peptone. According to Kiihne and Chit- 

 tenden, this is not further decomposed by trypsin. This is rather 

 remarkable, as on hydrolytic decomposition with mineral acids 

 gelatin yields leucin, aspartic acid, glutaminic acid, and considerable 

 amounts of glycocoll. Reich-Herzberger, however, has recently 

 announced that a slight formation of leucin takes place nevertheless 

 during the action of trypsin on gelatin. 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, 

 indol, or skatol from the substance, even on bacterial decomposition. 

 Diamino-groups, however, are largely present. 



The fact that neither elastin nor collagen (gelatin) give rise to 

 the formation of hetero-albumoses is of special interest in view of 



