232 PHYSIOLOGICAL CHEMISTRY. 



III. CARTILAGE. 



The principal .solid constituents of the matrix of cartilaginous 

 tissue are chrondromucoid, ckrondroitin-sulphuric acid, chrondroal- 

 bumoid and collagen. Chrondromucoid differs from the mucoids 

 isolated from other connective tissues in the large amount of chron- 

 droitin-sulphuric acid obtained upon decomposition. Besides being 

 an important constituent of all forms of cartilage, chrondroitin- 

 sulphuric acid has been found in bone, ligament, the mucosa of the 

 pig's stomach, the kidney of the ox, the inner coats of large arteries 

 and in human urine. It may be decomposed through the action of 

 acid and yields a nitrogenous body known as chrondroitin and later 

 this body yields chrondrosin. Chrondrosin is also a nitrogenous 

 body and has the power of reducing Fehling's solution more strongly 

 than dextrose. Sulphuric acid is a by-product in the formation of 

 chrondroitin, and acetic acid is a by-product in the formation of 

 chrondrosin. 



Chrondroalbumoid is similar in some respects to elastin and 

 keratin. It differs from keratin in being soluble in gastric juice and 

 in containing considerably less sulphur than any member of the 

 keratin group. It gives the usual protein color reactions. 



EXPERIMENTS ON CARTILAGE. 



1. Preparation of the Cartilage. Boil the trachea of an ox in 

 water until the cartilage rings may be completely freed from the 

 surrounding tissue. Use the cartilage so obtained in the following 

 experiments. 



2. Solubility. Cut 1 one of the rings into very small pieces and 

 try the solubility of the cartilage in the ordinary solvents (see page 



23). 



3. Millon's Reaction. 



4. Xanthoproteic Reaction. 



5. Hopkins-Cole Reaction. Conduct this test according to the 

 modification given on page 101. 



6. Test for Loosely Combined Sulphur. 



7. Preparation of Cartilage Gelatin. Cut the remaining carti- 

 lage rings into small pieces, place them in a casserole with water 

 and boil for several hours. Filter while the solution is still hot. 

 Observe that the filtrate soon becomes more or less solid. What 

 is the reason for this ? Bring a portion of the material into solution 

 by heat and try the following tests : 



