CHAPTER III. 



THE JUICES POURED OUT UPON THE FOOD AND THEIR 

 CHEMICAL CONSTITUENTS. 



i. The Saliva. This is the name applied to the mixed 

 secretions from the salivary glands and the mucous glands 

 of the mouth. The salivary glands are three in number, 

 the parotid, submaxillary, and sublingual, and as their secre- 

 tions differ somewliat they are best considered separately. 



Human parotid saliva can be obtained by introducing a 

 fine cannula into STENSON'S duct. In this way a clear, watery 

 liquid mixed with some epithelial cells and occasionally a 

 few leucocytes is obtained. The reaction is usually given 

 as faintly alkaline, but this seems to be - incorrect. It is 

 probably neutral, perhaps even slightly acid. 



The amount secreted in twenty-four hours varies within 

 wide limits physiologically. OHL gives 80 to 100 c.c. The 

 specific gravity varies under physiological conditions and is 

 stated to be between 1.006 and 1.012. The parotid secretion 

 contains mucin and only traces of proteins. It contains the 

 starch-splitting ferment amylase and the maltose-splitting 

 ferment maltase. It also contains sulphocyanic acid in com- 

 bination with the metals found universally in the tissue 

 fluids. The exact amount of each of these substances varies 

 under physiological conditions, so that it is not surprising 

 that the figures given by different investigators do not agree 

 very well. MITSCHERLICH found 14 to 16 parts, HOPPE- 

 SEYLER about 7 parts of solids in 1000 of parotid saliva. 

 About half of this amount is organic, the rest inorganic. 



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