EPITHELIAL AND CONNECTIVE TISSUES f 353 



III. CARTILAGE 



The principal solid constituents of the matrix 'of cartilaginous tissue 

 are chondromucoid, chondroitin-sulphuric acid, chondroalbumoid and 

 collagen. Chondromucoid differs from the mucoids isolated from 

 other connective tissues in the large amount of chondroitin-sulphuric 

 acid obtained upon decomposition. Besides being an important 

 constituent of all forms of cartilage, chondroitin-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 nitro- 

 genous body known as chondroitin and later this body yields chondrosin. 

 Chondrosin is also a nitrogenous body and has the power of reducing 

 Fehling's solution more strongly than dextrose. Levene and La Forge 1 

 claim the reducing action of chondrosin to be due to an hexosamine 

 isomeric with glucosamine. Sulphuric acid is a by-product in the forma- 

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



chondrosin. 



Chondroalbumoid 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 one of the rings into very small pieces and try the solubility 

 of the cartilage in water and dilute and concentrated acid and alkali. 



3. Mfflon's Reaction. 



4. Xanthoproteic Reaction. 



5. Glyoxylic Acid Reaction (Hopkins-Cole). -Conduct this test according to 

 the modification given on page 106. 



6. Test for Unoxidized Sulphur. 



7 Preparation of Cartilage Gelatin.-Cut the remaining cartilage 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 : 



(a) Biuret Test. 



(b) Test for Unoxidized Sulphur. 



(c) To about 5 c.c. of the solution in a test-tube add a few drops of banum 

 chloride. Do you get a precipitate, and if so to what is the precipitate due? 



i Levene and La Forge: Proc. Soc. ep. Biol. and Med., n, 124, 1914- 



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