CARTILAGE ,AND KERATIX BODIES. 349 



chondromucoid, chondroitin-sulphuric acid and an albuminoid. 

 The nature of crude collagen has been explained, and in 

 Chapter V the somewhat obscure chemistry of the chondroitin- 

 sulphuric acid has been outlined. Of the nature of the 

 chondromucoid little is known definitely; it has been held by 

 some writers to be merely a combination of part of the colla- 

 gen with the salts of the complex ethereal sulphuric acid men- 

 tioned, while Morner, who first described it, held it for a dis- 

 tinct body somewhat allied to mucin. His analyses showed 

 47.30, H 6.42, N 12.58, 82.42, 031.28. The sulphur is 

 probably all in the ethereal combination and on incineration 

 of the cartilage the ash is found to contain a very large amount 

 of alkali sulphate. 



Chondromucoid as separated is insoluble in water alone, but 

 with a little alkali forms a thick solution, which is precipitated 

 by acids. Stronger acids bring about a cleavage with separa- 

 tion of the chondroitin sulphuric acid. The weak alkali solu- 

 tions are precipitated by metallic salts, but most of the other 

 protein reactions fail. The ethereal sulphate group seems to 

 prevent the ordinary precipitations. 



The albuminoid substance is not well characterized but is 

 insoluble in water, and in weak acids or alkalies. It undergoes 

 gastric digestion. This protein is said to be found in old 

 cartilage only, and is absent in young cartilage. 



KERATIN BODIES. 



Compounds of the keratin group occur in hair, the finger 

 nails and horn. They resemble the proteins but contain 

 rather large amounts of sulphur, as shown by these analyses, 

 which are of keratin from several sources : 



