COLLAGENS. 119 



somewhat different physical properties among each other, but had about the same 

 elementary composition, with 0.34-0.53 per cent sulphur. SADIKOFF seems to 

 think that the gelatins prepared up to this time were perhaps not unit bodies 

 but were possibly mixtures. The bodies prepared by SADIKOFF from cartilage 

 he calls gluteins, because they were essentially different from the other gelatins 

 or glutins. They were poorer in carbon and nitrogen, 17.17 to 17.87 per cent, 

 but somewhat richer in sulphur, 0.53-0.718 per cent, than the tendon glutin. 

 The gluteins differ also from the glutins in that on boiling with a mineral acid 

 they have a faint reducing action, and also in that they give a color reaction 

 with phloroglucin-hydrochloric acid which is probably due to contamination. The 

 glutins differ from the gluteins by a different behavior with certain salts. 



The decomposition products of the collagens are the same as those of 

 the gelatins and will be found in the table on page 125. Of special 

 mention is the fact that gelatin contains no tyrosine and tryptophane 

 but does yield considerable glycocoll. This latter substance has, because 

 of its sweet taste, been called gelatin sugar. SKRAUP 1 has obtained on 

 the hydrolytic cleavage of gelatin a crystalline acid having the formula 

 Ci2H25N50io, which he calls glutinic add. Gelatin yields considerable 

 basic nitrogen, according to HAUSMANN, 2 35.83 per cent of the total 

 nitrogen. It also yields considerable arginine (9.3 per cent), lysine 5-6 

 per cent, but only little histidine (0.4 per cent) . The aromatic group in 

 gelatin is therefore, as directly shown by FISCHER and also by SriRO, 3 

 represented by phenylalanine. 



Collagen is insoluble in water, salt solutions, and dilute acids and 

 alkalies, but it swells up in dilute acids. By continued boiling with 

 water it is converted into gelatin. Various collagens are converted into 

 gelatin with varying readiness; the formation of gelatin occurs also 

 from difficultly soluble collagens by continuous boiling with water. 

 Collagen is dissolved by the gastric juice and also by the pancreatic 

 juice (trypsin solution) when it has previously been treated with acid 

 or heated with water above 70 C. 4 By the action of ferrous sulphate, 

 corrosive sublimate, or tannic acid, collagen shrinks greatly. Collagen 

 treated by these bodies does not putrefy, and tannic acid is therefore of 

 great importance in the preparation of leather. 



Gelatin or glutin is colorless, amorphous, and transparent in thin 

 layers. It swells in cold water without dissolving. It dissolves in warm 

 water, forming a sticky liquid, which solidifies on cooling when sufficiently 

 concentrated. As PAULI and RONA 5 have shown, various bodies may 

 have a different influence upon the gelatinization-point of a gelatin 



1 Monatshefte f. Chem., 26. 



2 Zeitschr. f. physiol. Chem., 27. 



3 Fischer, Levene and Aders, Zeitschr. f. physiol. Chem., 35; Spiro, Hofmeister's 

 Beitrage, 1. 



4 Kuhne and Ewald, Verb. d. Naturhist. Med. Vereins in Heidelberg, 1877, 1. 

 6 Hofmeister's Beitrage, 2. 



