FISH ISINGLASS AND GLUE. 



By Geokge p. White. 



COLLAGEN AND GELATIN. 



Collagen, the mother substance of gelatin, is an albuminoid which 

 occurs to a large extent in vertebrates and also in the flesh of cepha- 

 lopods. It is the chief constituent of the white fibrils of connective 

 tissue and is also found in bones, cartilages, ligaments, fish scales, etc. 

 Collagens of different origins are not of identical composition ; how- 

 ever, all show the characteristic albuminoid property of being in- 

 soluble in water and the ordinary protein solvents. 



The most interesting and commercially important property of 

 collagen is its power to be converted into gelatin by heating with 

 water alone or in the presence of dilute acids. On the other hand, 

 if gelatin is heated to 130° C. it is transformed back into collagen, 

 so that there is a very intimate relation between the two substances. 

 For practical purposes we may consider gelatin to be collagen which 

 has been converted into a soluble form by combination with water. 

 (Other changes have been noted, such as the evolution of ammonia, 

 when collagen is treated with water.) The following table gives the 

 composition of collagen, gelatins from various sources, and of fish 

 glue, which is a crude form of gelatin: 



Composition of Collagen and Gelatin. 



Nitrogen, 



Hydro- 

 gen. 



Sulphur. 



Oxygen. 



Collagen 



Gelatin from— 



Commercial source . 



. Tendons 



Ligaments 



Cartilage 



Trachea 



Ear 



Air bladder 



Fish scales 



Fish glue 



49.38 

 50.11 

 50.49 

 50.34 



Per cent. 

 17.86 



17,97 

 17.81 

 17.90 

 17.76 



17.87 



Per cent. 

 6.47 



6.56 

 6.71 

 6.96 



17.68 

 17.51 

 17.68 



0.7 



.26 

 .57 

 .58 

 .70 



Per cent. 

 a 24. 92 



25.13 

 25.26 

 24.33 



Includes sulphur; separate percentage not noted. 



