THE ALBUMINOIDS. 



73 



The following are some elementary analyses that have been made of 

 keratin from different sources : 



The main feature in the above analyses is the high percentage of 

 sulphur, 5 which is in part in loose combination, and can be removed by 

 alkalis or even by boiling water. 



An albuminoid obtainable from tracheal cartilage by C. T. Mb'rner, 

 and further investigated by Hedenius, 7 is included by Hammarsten 8 

 among the keratins, or as a substance intermediate between keratin and 

 coagulated proteid. It contains only 1 per cent, of sulphur. Keratin 

 gives the proteid reactions. 



Derivatives of keratin. Keratin is not digestible by either gastric 

 or pancreatic juice. By heating with water to 150-200 C. it dissolves, 

 forming a turbid solution. It dissolves more readily in alkalis ; the 

 solution contains alkaline sulphides, and substances of the proteose class, 

 called keratinoses by Krukenberg. 9 



The decomposition products of keratin obtained by the use of acids 

 are like those of the proteids, and include leucine, a good deal of tyrosine 

 (1-5 per cent.), aspartic acid, 10 glutaminic acid, 11 ammonia, and sul- 

 phuretted hydrogen, lysine, 12 lysatinine, 12 and a sulphur-containing sub- 

 stance 12 which forms a compound with hydrochloric acid, with the 

 formula C 14 H 38 N 4 12 SC1 4 . Drechsel 13 considers that some of the oxygen 

 of the keratin is united to sulphur, and a part to amido-acid radicles. 



The close chemical relationship of keratin to proteid coincides with 

 what is known as to its formation within the protoplasm of cells, for 

 instance in the epidermis. The eleidin granules of the stratum granulosum 

 probably represent an intermediate stage in the transformation. 



1 Ann. d. Ghem., Leipzig, Bd. xlv. 

 " Versuch. einer allgem. physiol. Chem.," Braunschweig, 1844-51. 



3 Kiiline and Chittenden, loc. cit. 



4 See Drechsel, Ladenbnrg's "Handworterbuch," Bd. iii. Other analyses of horn have 

 been made by Tilanus, Hoppe-Seyler's "Physiol. Chem.," S. 90 ; Liiulvall, Jahresb. u. d. 

 Fortschr. d. Thier-Chem., Wiesbaden, 1881. 



5 A large number of estimations of sulphur in keratins from different sources will be 

 found in a paper by Mohr, Ztschr. f. physiol. Chem., Strassburg, 1895, Bd. xx. S.-403. 

 The percentage varies from 2'6 to 5'3. During (ibid., 1896, Bd. xxii. S. 281) obtained very 

 similar results. 



6 Jahresb. il. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xviii. S. 217. 



7 Skandin. Arch. f. Physiol., Leipzig, Bd. iii. 



8 "Physiol. Chem.," 3rd German edition. S. 44. 



9 Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naturu:, 1886. 



10 Kreusler, Journ. f. prakt. Chem., Leipzig, Bd. cvii. 



11 Horbaczewski, Sitzungsb. d. k. Akad. d. Wissensch., Wien, Bd. Ixxx. 



13 Hedin, Jahresb. il. d.' Fortschr. d. Thier-Chem., W 7 iesbaden, 1893, Bd. xxii. 

 13 Loc. cit. 



