GASTRIC JUICE 249 



These substances may be separated one from another by fractional pre- 

 cipitation with ammonium sulphate. Those precipitated by a degree of satura- 

 tion of twenty-four to forty- two per cent are called primary albumoses (hetero- 

 albumose, protoalbumose). Those precipitated by stronger concentration of 

 the sulphate are designated deuteroalbumoses. Those easily diffusible prod- 

 ucts not precipitated by the salt, but still giving the biuret reaction,, are known 

 as peptones. After acidification of the solution the peptones, in an impure 

 condition, can be separated from other end products by precipitation with 

 picric acid. 



We have then from peptic cleavage of proteid (besides acid albuminate) 

 first, two primary albumoses (hetero- and protoalbumose), and then deutero- 

 albumose (Pick, Zunz). Primary albumoses show a higher percentage of 

 C and N and a lower percentage of than the original proteid (e. g., in 

 fibrin, there are 52.7 per cent C, 16.9 per cent N, 1.1 per cent S, and 22.5 per 

 cent 0, while in the primary albumoses derived from it we find 55.4 per cent 

 C, 17.8 per cent N", 1.2 percent S, and 19.1-18.7 per cent 0). Heteroalbu- 

 mose from fibrin contains thirty-nine per cent of the total nitrogen in basic 

 form and fifty-seven per cent as monoamino acids, while the corresponding 

 numbers for protoalbumose are twenty-five and sixty-eight per cent respec- 

 tively. Heteroalbumose contains only a small quantity of the aromatic groups 

 which yield tyrosin and indol, but it is rich in those groups which yield leucin 

 and glycocoll. Protoalbumose, on the other hand, yields abundance of tyrosin, 

 indol and skatol, but only a little leucin and no glycocoll. 



The third direct product of digestion is a deuteroalbumose (synalbumose) 

 which is characterized chiefly by the fact that it contains a carbohydrate group, 

 whenever such a group occurs in the parent proteid molecule. Its quantita- 

 tive composition differs materially from that of the primary albumoses:' thus 

 48.7 per cent C, 13.8 per cent N, 30.5 per cent S + 0. 



On further cleavage with pepsin, primary albumoses yield secondary albu- 

 moses which appear to be very numerous. Among them thioalbumose should 

 be especially mentioned on account of its high content of S (three per cent). 



Deuteroalbumoses are transformed into peptones, the molecular weight 

 of which is relatively small only about 500 by the depression of the freezing 

 point, whereas the molecular weight of deuteroalbumose is about 3,200. 



According to Kiihne, peptic cleavage of proteid could proceed only as far 

 as the formation of peptones. Later it was found that from the beginning of 

 the cleavage, substances separate off which no longer give the biuret reaction. 

 Among these are certain intermediary substances, the peptoids, comparable in 

 their structure to the peptones, from which after long-continued digestion the end 

 products finally appear. Probably all of the hydrolytic cleavage products (cf. 

 page 72) belong here, for already the following have been demonstrated in such 

 digestive mixtures: leucin, asparatic acid, cadaverin, putrescin, glutamic acid, 

 tyrosin, amino-valerianic acid, dihexosamin, lysin, penta-methyl-endiamin, phe- 

 nylalanin, cystin, a-pyrrolidin-carboxylic acid, tryptophan (Pfaundler, Lawrow, 

 Langstein, Salaskin, Fischer, and Abderhalden). 



The relative proportion of primary digestive products obtained from dif- 

 ferent kinds of proteids is very different. The kind of albumoses formed is 



