384 THE SUPPORTING TISSUES. 



tissue the matrix here also consists essentially of water and some 

 mucinous substance. Whether or not this is identical with the so- 

 called chondromucoid, which can be obtained from the cartilage of 

 the adult animal, is not known. 



A general idea of the chemical composition of cartilage may be 

 formed from the following analyses, which are taken from His : 



Costal cartilage Articular cartilage 



(human). from knee-joint (human). 

 Water ........... 67.67 per cent. 73,59 per cent. 



Solids ........... 32.33 " " 26.41 " " 



Organic material .... 30.13 " " 24.87 " " 



Mineral salts ...... 2.20 " " 1.54 " " 



Analysis of the mineral salts has given the following results 

 (calculated for 100 parts of the mineral ash) : 



Sodium chloride ...... 6.11 per cent. 22.48 per cent. 



Sodium sulphate ...... 44.81 " " 55.17 " " 



Potassium sulphate ..... 26.66 " " 



Sodium phosphate ..... 8.42 " " 7.39 " " 



Calcium phosphate ..... 7.88 "I (( l( 15^1 " " 



Magnesium phosphate . . . 4.55 / 



The organic constituents of the cartilaginous matrix are essentially 

 represented by chondroitin-sulphuric acid as such, and its compounds 

 with collagen and albumins. In addition, a small amount of soluble 

 albumins is found, as also a peculiar insoluble albuminous sub- 

 stance, which has been termed albumoid. 



Chondroitin-sulphuric Acid. This substance is a conjugate 

 sulphate, and, according to Schmiedeberg, has the composition 

 C 18 H 27 NO 14 .SO 3 . On hydrolytic decomposition it yields a hyalin, 

 chondroitin, which in turn gives rise to the formation of chondrosin, 

 and this to glucuronic acid and glucosamin, as represented by the 

 equations : 



(1) C I8 H ?7 NO U .S0 3 + H 2 == C )8 H 27 N0 14 + H 2 SO, 



Chondroitin-sulphuric Chondroitin. 



acid. 



(2) C 18 H 27 NO U + 3H 2 O = C 12 H 21 NO n + 3CH. r COOH 



Chondroitin. Chondrosin. Acetic acid. 



(3) C, 2 H ?1 NO U + H 2 O = COOH(CH.OH) 4 .COH 



Chondrosin. Glucuronic Glucos- 



acid. amin. 



Both chondroitin and chondrosin are monobasic acids. The latter 

 reduces Fehling's solution directly, while in the case of chondroitin 

 this occurs only after the substance has been decomposed. 



Chondroitin-sulphuric acid is an amorphous substance, and is 

 soluble in water. A concentrated solution resembles mucilage in 

 appearance and consistence. Its salts are also for the most part 

 soluble in water. The sodium and potassium salts can be pre- 

 cipitated by means of ferric chloride, lead subacetate, and alcohol, 

 while silver nitrate, zinc chloride, tannic acid, and potassium f'crro- 

 cyanide, the latter in the presence of acetic acid, are without effect. 



