COLLAGEN. 117 



On account of its great resistance to chemical reagents, eiastin may 

 be prepared (best from the ligamentum nuchiE) in the following way: 

 First boil with water, then with 1 per cent caustic potash, then again 

 with water, and lastly with acetic acid. The residue is treated with cold 

 5 per cent hydrochloric acid for twenty-four hours, carefully washed with 

 water, boiled again with water, and then treated with alcohol and ether. 



In regard to the methods used by SCHWARZ and by RICHARDS and GIES, which 

 are somewhat different, we refer to the original publications. 



Collagen, or gelatin-forming substance, occurs very extensively in 

 vertebrates. The flesh of cephalopods is also said to contain collagen. 1 

 Collagen is the chief constituent of the fibrils of the connective tissue and 

 (as ossein) of the organic substances of the bony structure. It also occurs 

 in the cartilaginous tissues as chief constituent; but it is here mixed with 

 other substances, producing what was formerly called chondrigen. Col- 

 lagen from different tissues has not quite the same composition, and 

 probably there are several varieties of collagen. 



By continued boiling with water (more easily in the presence of a 

 little acid) collagen is converted into gelatin. HoFMEiSTER 2 found that 

 gelatin on being heated to 130 C. is again transformed into collagen; and 

 this last may be considered as the anhydride of gelatin. Collagen and 

 gelatin have about the same composition. 3 



c H N s o 



Collagen 50 . 75 6 . 47 17 . 86 24 . 92 (HOFMEISTER) 



Gelatin (commerical) .... 49.38 6.80 17.97 0.7 25.13 (CHITTENDEN) 



Gelatin from tendons 50.11 6.56 17.81 0.26 25.26 (VAN NAME) 



Gelatin from ligaments ... 50.49 6.71 17.90 0.57 24.33 (RICHARDS and GIES) 



Fish glue (isinglass) 48.69 6.76 17.68 (FAUST) 



Gelatins of different origin show a somewhat variable composition, 

 which seems to indicate the occurrence of different collagens. It is diffi- 

 cult to say whether the variable content of sulphur is due to a contam- 

 ination with a substance rich in sulphur or to a splitting off of loosely 

 combined sulphur during the purification. C. MORNER* has prepared 

 a typical gelatin containing only 0.2 per cent of sulphur by a method 

 which eliminated any possible changes due to reagents. 



SADIKOFF 5 has prepared gelatins by various methods from tendons and 

 from cartilage. Those from tendons, some of which were prepared after pre- 

 vious tryptic digestion, some after treatment with 0.25 per cent caustic potash, 



1 Hoppe-Seyler, Physiol. Chem., p. 97. 



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



3 Hofmeiser, 1. c.; Chittenden and Solley, Journ. of Physiol., 12; van Name, Journ. 

 of Exper. Med., 2; Richards and Gies, Amer. Journ. of Physiol., 8; Faust, Arch. f. 

 exp. Path. u. Pharm., 41. 



4 Zeitschr. f. physiol. Chem., -28. 



5 Ibid., 39 and 41. 



