The Gelatin from White Fibrous Connective Tissue

In a general way the chemical nature and composition of gelatin have been established for many years, but the more thorough chemical study of various forms of connective tissue, which has been carried on so successfully during the last decade, has revealed the existence of at least three distinct varieties of collagen, characterized by marked differences in chemical composition. The collagen of white fibrous tissue and of bone is generally considered as the same; it apparently yields on hydration a gelatin with about 18 per cent of nitrogen. The collagen which makes up the greater portion of the cornea, on the other hand, contains about 17 per cent of nitrogen,* while the collagen of cartilage t yields a gelatin with only 16 per cent of nitrogen. Furthermore, we have evidence of the existence of a body in reticular tissue reticulin--the composition of which appears to lie midway between that of gelatin and of elastin. $ Its nitrogen-content, sccording to Siegfried, is 15.63 per cent. Again, the amount of sulphur in gelatin is usually placed at about 0.6 per cent,§ Out the gelatin formed from corneal collagen contains o~ly 0.3 per cent of this elernent.l[ Lastly, Schiitzenberger and Burgeois consider gelatin (commercial gelatin) as practically free from sulphur, or hold at least that this ele: ment is an unessential constituent of the molecule.¶