5 PHYSIOLOGICAL CHEMISTRY. 



EXPERIMENTS ON SALIVA. 



A satisfactory method of obtaining the saliva necessary for the 

 experiments which follow is to chew a small piece of pure paraffin 

 wax, thus stimulating the flow of the secretion, which may be col- 

 lected in a small beaker. Filtered saliva is to be used in every ex- 

 periment except for the microscopical examination. 



1. Microscopical Examination. Examine a drop of unfiltered 

 saliva microscopically and compare with Fig. 18 below. 



2. Reaction. Test the reaction to litmus. 



FIG. 1 8. 



MICROSCOPICAL CONSTITUENTS OF SALIVA. 



a, Epithelial cells ; b, salivary corpuscles ; c, fat drops ; d, leucocytes ; e, f and g^ 

 bacteria ; h, i and k, fission-fungi. 



3. Specific Gravity. Partially fill a urinometer cylinder with 

 saliva, introduce the urinometer, and observe the reading. 



4. Test for Mucin. To a small amount of saliva in a test-tube 

 add 1-2 drops of dilute acetic acid. Mucin is precipitated. 



5. Biuret Test. 1 Render a little saliva alkaline with an equal 

 volume of KOH and add a few drops of a very dilute (2-5 drops in 

 a test-tube of water) cupric sulphate solution. The formation of 

 a purplish-violet color is due to mucin. 



6. Millon's Reaction. 2 Add a few drops of Millon's reagent to 

 a little saliva. A light yellow precipitate formed by the mucin 

 gradually turns red upon being gently heated. 



7. Preparation of Mucin. Pour 25 c.c. of saliva into 100 c.c. 

 f 95 P er cent alcohol, stirring constantly. Cover the vessel and 

 allow the precipitate to stand at least 12 hours. Pour off the 

 supernatant liquid, collect the precipitate on a filter and wash it, in 



1 The significance of this reaction is pointed out on page 92. 



2 The significance of this reaction is pointed out on page go. 



