THE PROTEIN SUBSTANCES. 39 



juice or trypsin solution, gelatine loses the property of gelatin- 

 izing and is transformed into gelatine-peptone. 



According to HOFMEISTER it splits into two substances, semiglutin and 

 hemicollin. The former is insoluble iu alcohol of 70-80$, and is precipitated 

 by platinum chloride. The latter, which is not precipitated by platinum 

 chloride, dissolves in alcohol. 



Collagen may be obtained from bones by extracting with hydro- 

 chloric acid (which dissolves the earthy matters) and then carefully 

 removing the acid with water. It may be obtained from tendons 

 treated with lime-water (which dissolves the albumin and mucin), 

 and then thoroughly washing with water. Gelatine is obtained by 

 boiling collagen with water. The finest commercial gelatine con- 

 tains a little albumin, which may be removed by allowing the finely- 

 divided gelatine to swell in cold water and extracting thoroughly 

 with large quantities of fresh water. In regard to the preparation 

 of gelatine from cartilage see Chapter VIII. 



Chondrin is only a mixture of glue with the specific constituents of cartilage 

 and their transformation products. Spongin forms the great mass of the ordi- 

 nary sponge. It gives no gelatine, and on boiling with acids it yields leucin 

 and glycocoll, but no tyrosiu. Conchiolin is found in the shells of mussels 

 and snails, and also in the egg-shells of these animals. It yields leuciu but no 

 tyrosin. Byssus contains a substance, closely related to conchiolin, which is 

 soluble with difficulty. Cornein forms the axial system of the Antipathes and 

 Gorgonia. It gives leucin and a crystallizable substance, cornicrystallin (KRU- 

 KENBERG). Fibroin and Sericin are the two chief constituents of raw silk. 

 By the action of superheated water the sericin dissolves and gelatinizes on 

 cooling (silk gelatine), while the more difficultly soluble fibroin remains un- 

 dissolved in the shape of the original fibre. On boiling with acid the fibroin 

 yields alanin (WEYI,), glycocoll, and a great deal (5-8$) of tyrosin. Fibroin is 

 dissolved in cold concentrated hydrochloric acid with the expulsion of \% ni- 

 trogen as ammonia, and it is converted into another, nearly-related substance 

 called sericoin (WfiYL). Sericin yields no glycocoll but leucin and a crystal- 

 lizable substance called serin. The composition of the above-mentioned 

 bodies is as follows : 



C H N S O 



Conchiolin (from snail-eggs) 50.92 6.88 17.86 0.31 24.34 (KRUKENBERG ) 



Spongin 46.50 6.30 16.20 0.5 27.50 (CROOCKEWITT.) 



48.75 6.35 16.40 (POSSELT.) 



Cornein 48.96 5.90 1681 .... 28.33 (KRUKENBERG.) 



Fibroin 48.23 6.27 18.31 .... 27.19 (CRAMER.) 



Sericin 44.32 6.18 18.30 .... 80.20 (CRAMER.) 



Amyloid, so called by VIRCHOW, is a protein substance appear- 

 ing under pathological conditions in the internal organs, such as 

 the spleen, liver, and kidneys, as infiltrations ; and in serous mem- 

 branes as granules with concentric layers. It probably also occurs 

 as a constituent of a few prostate calculi. Amyloid has not been 



