118 THE PROTEIN SUBSTANCES. 



and some after treatment with sodium hydroxide and then carbonate, showed 

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

 elementary composition, with 0.30-0.526 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 somehwat richer in sulphur, 0.53-0.712 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. 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 124. Of special 

 mention is the fact the gelatin contains no tyrosine but does yield con- 

 siderable glycocoll. This latter substance has, because of its sweet 

 taste, been called gelatin sugar. SKRAUP 1 has obtained on the hydro- 

 lytic cleavage of gelatin a crystalline acid having the formula C^H^NsOio, 

 which he calls glutinic acid. Gelatin yields considerable basic nitro- 

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

 DRECHSEL and FISCHER found lysine; HEDIN, KOSSEL and KUTSCHER S 

 found arginine also, which amounted to 9.3 per cent (KossEL and 

 KUTSCHER). On putrefaction gelatin gives neither tyrosine, indol, nor 

 skatol. According to SELTRENNY 4 it yields phenylpropionic acid and 

 phenylacetic acid. The aromatic group in gelatin is therefore, as 

 directly shown by FISCHER and also by SPIRO, S represented by phenyl- 

 alanine. 



On the oxidation of gelatin with potassium permanganate, SEEMANN obtained 

 besides volatile fatty acids (formic, acetic, butyric acids), benzoic acid, oxalic 

 acid, succinic acid, oxaluramide and probably also oxaluric acid. ZICKGRAF * 

 produced guanidine from the arginine. 



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 



1 Monatshefte f. Chem., 26. 



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



3 Drechsel, Arch. f. Anat. u. Physiol., 1891; Hedin, Zeitschr. f. physiol. Chem., 21; 

 Kossel and Kutscher, ibid., 31. 



4 Monatshefte f . Chem., 10. 



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

 Beitrage, 1. 



e Seemann, Zeitschr. f. physiol. Chem., 44; Zickgraf, ibid., 41. 



