1202 CHONDRIK 



solution by the action of superheated water on hyaline carti- 

 lage, exhibits the following characteristic reactions. It is pre- 

 cipitated by acetic acid which does not, even if in considerable 

 excess, redissolve the precipitate ; minute quantities of mineral 

 acids similarly cause a precipitate to appear which is in this 

 case readily soluble in the slightest excess of the acids. These 

 reactions suffice to distinguish between chondrin and gelatin, 

 and a further distinction may be made on the basis of the fact 

 that solutions of chondrin are precipitated by several reagents 

 such as alum, normal lead acetate, and other metallic salts (of 

 Ag and Cu), which yield no precipitate with gelatin, while on 

 the other hand mercuric chloride and tannin do not precipitate 

 chondrin but are characteristic precipitants of gelatin (see 

 above). The above reactions also indicate a possible relation- 

 ship to mucin, which is confirmed by the fact that chondrin 

 when boiled with dilute mineral acids yields a reducing sub- 

 stance with marked carbohydrate affinities. Hence the view 

 was some years ago expressed that chondrin is not a definite 

 unitary substance, but a mixture of gelatin and mucin, and 

 recent research has confirmed the general accuracy of this 

 statement. The following is a somewhat synoptic account 

 of the views now held as to the chemistry of cartilage. By 

 appropriate methods of extraction, of which the details are too 

 complicated to admit of any adequately concise description, the 

 matrix of cartilage yields a substance with marked affinities to 

 mucin, and hence called chondromucoid. This resembles mucin 

 in several of its reactions and like mucin yields, when boiled 

 with mineral acids, a form of acid-albumin and a reducing 

 body. The latter is not an immediate product of the decom- 

 position of the chondromucoid, but makes its appearance in the 

 final stage of the cleavage of the products first formed. When 

 boiled with acids chondromucoid yields at first an acid called 

 chondroitic acid, of which a certain amount is also present in 

 the free state in the cartilage and may be extracted from it by 

 means of dilute caustic soda. Chondroitic acid is regarded as 

 being an ethereal sulphate of a substance called chondroitin, 

 and the latter when boiled with mineral acids splits up into 

 acetic acid and the above-mentioned reducing substance now 

 named chondrosin, to which the formula C 12 H 21 NO n is assigned. 

 Chondrosin is soluble in water, hevorotatory, reduces cupric 

 oxide in an alkaline solution somewhat more strongly than 

 does glucose, has thus marked carbohydrate affinities, and from 

 the products obtained when it is decomposed by barium hydrate 

 may perhaps be regarded constitutionally as similar to a com- 

 pound of glycuronic acid (see p. 1220) and glucosamine (see 

 p. 1205). The residue of cartilage which remains after the 

 extraction of chondromucoid consists chiefly of a collagenous 

 substance which by the action of superheated water, as in a 



