510 TISSUES YIELDING GELATIN. 



volatile bases : methylamine, di- and trimethylamine, 

 pyridin, etc.* When distilled with manganese per- 

 oxide, or potassium bichromate and sulphuric acid, 

 gelatin yields the same numerous products as the pro- 

 tein compounds under similar treatment (p. 486). 



When a solution of gelatin is boiled with sulphuric 

 acid or potassa, there are produced, besides ammonia 

 and some not well known products, glycocol (p. 85), 

 and leucine (p. 98). 



Chondrin is produced from permanent (non-oss : fy- 

 ing) cartilages, as from the cartilages of the ribs, the 

 joints, bronchi, nose, from the cornea, from bone- 

 cartilage before ossification, by boiling with water. 

 Its solution congeals on cooling, like that of ordinary 

 gelatin ; in a dried condition it looks like the latter, 

 but its solution is not only precipitated by tannic 

 acid, but by acetic and hydrochloric acids, dilute sul- 

 phuric acid, alum, lead acetate, and iron sulphate ; all 

 of which do not precipitate glutin. The precipitate 

 with alum forms large, compact, white flocks, soluble 

 in an excess of alum and several other salt solutions. 

 The precipitates with hydrochloric and sulphuric 

 acids, but not that with acetic acid, are easily redis- 

 solved in an excess of the precipitating substance. 

 On combustion, chondrin likewise leaves behind earthy 

 matter. It contains between 14 and 15 per cent, of 

 nitrogen and a small quantity of sulphur. 



Its decomposition-products are the same as those of 

 glutin ; by boiling with sulphuric acid, however, only 

 leucine, but no glycocol, is formed. "When boiled with 

 hydrochloric acid, it } 7 ields a fermentable sugar. 



The gelatin from the bones of placoidians differs from 

 the two other varieties of gelatin in the fact that its 

 solution does not gelatinize ; otherwise it conducts 

 itself like chondrin. 



In silk is contained a peculiar body, fibroin, 

 C 15 H 23 N 5 6 , which constitutes about 66 per cent, of 



* These volatile bases are contained in the substance called Oleum 

 animale Dippelii. It is obtained by rectification of fetid animal oil, which 

 is a by-product in the preparation of bone-black on the large scale, 

 from boues free of fat (see Pyridin bases, p 180). 



