THE SALIVA. 



141 



Physical and Chemical Properties of the Saliva Human saliva, 

 obtained directly from the cavity of the mouth, is a colorless, slightly 

 viscid, and alkaline fluid, with a specific gravity of 1.005. When first 

 discharged, it is frothy and opaline, holding in suspension minute whitish 

 flocculi. On being allowed to stand for some hours in a cylindrical glass 

 vessel, an opaque, whitish de- 

 posit collects at the bottom, 

 while the supernatant fluid be- 

 comes clear. The deposit, when 

 examined by the microscope 

 (Fig. 38), is seen to consist of 

 abundant epithelium scales 

 from the internal surface of 

 the mouth, detached by me- 

 chanical attrition, minute, 

 roundish, granular, nucleated 

 cells, apparently epithelium 

 from the mucous follicles, a 

 certain amount of granular 

 matter, and a few oil-globules. 

 The supernatant fluid has a 

 faint bluish tinge, and becomes 

 slightly opalescent by boiling, 

 or by the addition of nitric 

 acid. Alcohol in excess causes the precipitation of abundant whitish 

 flocculi. 



According to the analyses of Bidder and Schmidt, the composition 

 of the saliva is as follows : 



BTTCCAL AND GLANDULAR EPITHELIUM, 

 with Granular Matter and Oil-globules; deposited 

 as sediment from human saliva. 



COMPOSITION OF THE SALIVA. 



995.16 



Albuminous matter 1.34 



Potassium sulphocyanide 0.06 



Calcareous, magnesian, and alkaline phosphates . . 0.98 



Sodium and potassium chlorides 0.84 



Mixture of epithelium 1.62 



1000.00 



It will be seen that the saliva is one of the least concentrated of the 

 digestive secretions, containing but a very small quantity of organic 

 matter, and by no means a large proportion of mineral salts ; its watery 

 ingredient being by far the most abundant, as compared with the other 

 animal fluids. The albuminous matter of the saliva consists of a small 

 quantity of albumen, coagulable by the ordinary means ; more or less 

 mucosine, which gives to the fluid its slightly viscid character; and 

 ptyaline, a substance peculiar to the saliva, which is not coagulated, 

 like albumen, by nitric acid or potassium ferrocyanide, but is precipi- 



