CHAP. I.] MIXED SALIVA. 17 



during mastication at the rate of 1300 grammes of saliva for each 

 100 grammes of gland-substance, the saliva containing 6'3 grammes 

 of solid constituents, of which >3'9 grammes consist of organic matters. 



Physical Properties of Mixed Saliva. 



Normal saliva is, when perfectly fresh, a clear, transparent, viscid 

 fluid, which on microscopic examination is found to hold in suspension, 

 but very sparsely distributed through it, cells of squamous epithelium 

 which have become detached from the walls of the mouth, besides 

 certain cells denominated salivary corpuscles, which are probably 

 leucocytes altered by the action of saliva ; these cells, which present 

 some resemblance to leucocytes, are much more globular and contain 

 within their interior granules which exhibit so-called Brownian 

 movements in a very remarkable manner. 



specific The specific gravity of the mixed saliva of man 



gravity. varies between T002 and T006, the mean being, how- 



ever, about 1-003. 



Reaction. Perfectly normal, human saliva possesses an alkaline 



reaction, which is least marked after a long fast, and most distinct 

 when the flow of the secretion is at its height. According to 

 Chittenden and Smith the alkalinity corresponds to that of a solution 

 containing 0'08 per cent, of Na 2 C0 3 1 . 



In some persons, especially in the morning, the saliva is found to 

 possess an acid reaction, which is however due to fermentative changes. 

 Frerichs 2 found that 100 grammes of saliva secreted by himself, 

 during smoking, required 0150 grammes of sulphuric acid to neu- 

 tralise it. 



THE CHEMICAL CONSTITUENTS OF MIXED SALIVA. 



Water. A.S is indicated by its specific gravity, saliva is a 



very watery liquid, containing only from five to six parts per mille 

 of solid constituents. 



The Organic Solids of Saliva. 



Proteids The solids consist partly of undissolved, suspended, 



and mucin. organic matters, especially epithelium, and partly of 

 dissolved organic matters and salts. They always contain a very 

 small quantity of a soluble proteid, which resembles, if it is not 

 identical with, serum-albumin, besides a considerable quantity of 

 mucin. 



Diastatic In the case of the saliva of man and certain other 



enzyme. animals, an enzyme is present which possesses amylolytic 



properties and exerts a chemical action which appears to be identical 



1 Chittenden and Smith, Transactions Connecticut Association, 1885. 



2 Freriehs, Article 'Verdauung,' Wagner's Handworterbuch der Physiologic, Vol. 

 ii. Part i. p. 760. 



G. 2 



