EPITHELIAL AND CONNECTIVE TISSUES. 233 



(a) Biuret Test. 



(b) Bardach's Reaction. 



(c) Test for Loosely Combined Sulphur. 



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

 drops of barium chloride. Do you get a precipitate, and if so to 

 what is the precipitate due ? 



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

 drops of dilute hydrochloric acid and boil for a few moments. 

 Now add a little barium chloride to this solution. Is the precipi- 

 tate any larger than that obtained in the preceding experiment? 

 Why? 



(/) To the remainder of the solution add a little dilute hydro- 

 chloric acid and boil for a few moments. Cool the solution, neu- 

 tralize with solid potassium hydroxide and try Fehling's test. Ex- 

 plain the result. 



IV. OSSEOUS TISSUE. 



Bone is composed of about equal parts of organic and inorganic 

 matter. The organic portion, called ossein, may be obtained by 

 removing the inorganic salts through the medium of dilute acid. 

 Ossein is practically the same body which is termed collagen in 

 the other connective tissues, and in common with collagen yields 

 gelatin upon being boiled with dilute mineral acid. 



In common with the other connective tissues bone contains a 

 mucoid and an albumoid. Because of their origin these bodies 

 are called osseomucoid and osseoalbumoid. Osseomucoid, when 

 boiled with hydrochloric acid, yields sulphuric acid and a sub- 

 stance capable of reducing Fehling's solution. The composition 

 of osseomucoid is very similar to that of tendomucoid and chron- 

 dromucoid (see page 106). 



EXPERIMENT ON OSSEOUS TISSUE. 



Analysis of Bone Ash. Take one gram of bone ash in a small 

 beaker and add a little dilute nitric acid. What does the effer- 

 vescence indicate? Stir thoroughly and when the major portion 

 of the ash is dissolved add an equal volume of water and filter. 

 To the acid filtrate add ammonium hydroxide to alkaline reaction. 

 A heavy white precipitate of phosphates results. (What phos- 

 phates are precipitated here by the ammonia?) Filter and test the 

 filtrate for chlorides, sulphates, phosphates and calcium. Add 

 dilute acetic acid to the precipitate on the paper and test this filtrate 



