EPITHELIAL AND CONNECTIVE TISSUES. 229 



about the tendon and cut the clean tendon into small pieces. Wash 

 the pieces in water, changing the wash water often in order to 

 remove as much as possible of the soluble protein and inorganic 

 salts. Transfer the washed pieces of tendon to a flask and add 

 300 c.c. of Jialf -saturated lime water. 1 Shake the flask at intervals 

 for twenty-four hours. Filter off the pieces of tendon and pre- 

 cipitate the mucoid with dilute hydrochloric acid. Allow the mu- 

 coid precipitate to settle, decant the supernatant fluid and filter the 

 remainder. Test the mucoid as follows. 



(a) Solubility. Try the solubility in the ordinary solvents (see 

 page 23). 



(b) Biuret Test. First dissolve the mucoid in potassium hydrox- 

 ide solution and then add a dilute solution of cupric sulphate. 



(c) Test for Loosely Combined Sulphur. 



(d) Hydrolysis oi Tendomucoid. Place the remainder of the 

 mucoid in a small beaker, add about 30 c.c. of water and 2 c.c. 

 of dilute hydrochloric acid and boil until the solution becomes dark 

 brown. Cool the solution, neutralize it with solid potassium hy- 

 droxide and test by Fehling's test. With a reduction of Fehling's 

 solution and a positive biuret test what do you conclude regarding 

 the nature of tendomucoid? 



2. Collagen. This substance is present in the tendon to the ex- 

 tent of about 32 per cent. Therefore in making the following 

 tests upon the pieces of tendon from which the mucoid, soluble 

 protein and inorganic salts were removed in the last experiment, 

 we may consider the tests as being made upon collagen. 



(a) Solubility. Cut the collagen into very fine pieces and try 

 its solubility in the ordinary solvents (see page 23). 



(b) Milloris Reaction. 



(c) Biuret Test. 



(d) Xanthoproteic Reaction. 



(e) Hopkins-Cole Reaction. 



(/) Test for Loosely Combined Sulphur. Take a large piece 

 of collagen in a test-tube and add about 5 c.c. of potassium hy- 

 droxide solution. Heat until the collagen is partly decomposed, 

 then add 1-2 drops of plumbic acetate and again heat to boiling. 



(g) Formation of Gelatin from Collagen. Transfer the remain- 

 der of the pieces of collagen to a casserole, fill the vessel about two- 

 thirds full of water and boil for several hours, adding water at 



1 Made by mixing equal volumes of saturated lime-water and water from the 

 faucet. 



