KERATINS. 113 



It seems that there exist a number of keratins, and these form a special 

 group of bodies. This fact, together with the difficulty in isolating the 

 keratin from the tissues in a pure condition without a partial decom- 

 position, is sufficient explanation for the variation in the elementary 

 composition given below. As examples the analyses of a few tissues 

 rich in keratin and of keratins are given: 1 



MoHR 2 has determined the quantity of sulphur in various keratin 

 substances. Sulphur is in great part in loose combination, and it is 

 removed principally by the action of alkalies (as sulphides), or indeed in 

 part by boiling with water. Combs of lead after long usage become black, 

 and this is due to the action of the sulphur of the hair. On heating keratin 

 with water in sealed tubes to a temperature of 150 C. or higher, it dis- 

 solves with the elimination of sulphureted hydrogen or mercaptan 

 (BAUER), and the solution contains proteose-like substances (KRUKEN- 

 BERG) called atmidkeratin and atmidkeratose by BAUER. 3 Keratin is 

 dissolved by alkalies, especially on warming, producing besides alkali 

 sulphides also proteose substances. 



Besides the well-known cleavage products such as leucine, tyrosine, 

 aspartic acid, glutamic acid, arginine, and lysine, FISCHER and DORPING- 

 HAUS, 4 have found glycocoll, alanine, valine, proline, serine, phenyla- 

 lanine, and pyrrolidone-carboxylic acid (secondary from glutamic acid) 

 among the cleavage products of horn substances. EMMERLING claims 

 to have found cystine as a sulphurized cleavage product, but K. MORNER 



1 Rutherford and Hawk, Journ. of biol. Chem., 3; Mulder, Versuch einer allgem. 

 physiol. Chem., Braunschweig, 1844-51; Kiihne, Zeitschr. f. Biologic, 26; Horbaczew- 

 ski, see Drechsel in Ladenburg's Handworterbuch. d. Chem., 3; Lindvall, Maly's 

 Jahresbericht, 1881; Argiris, Zeitschr. f. physiol. Chem., 54; Pregl., ibid., 56. 



2 Zeitschr. f. physiol. Chem., 20. 



3 Krukenberg, Untersuch. tiber d. chem. Bau d. Eiweisskorper, Sitzungsber. d. 

 Janaischen Gesellsch. f. Med. u. Naturwissensch., 1886; Bauer, Zeitschr. f. physiol. 

 Chem., 35. 



4 Zeitschr. f. physiol. Chem., 36, which contains also the older literature. 



