INSALIVATION. 181 



and 1.0033. The solids are from 3.6 to 4.6 parts per -1000. It 

 contains ptyaliu, but authorities differ as to its containing potas- 

 sium sulphocyanate. 



The existence of such ducts as those of Stenson and Wharton 

 makes it easy to obtain the pure secretions of the parotid and 

 submaxillary glands by the introduction into them of cannulae ; 

 but this is not true of the sublinyual gland, hence the secretion from 

 this gland in man has never been obtained in sufficient quantity 

 to make a thorough analysis of it, but it is known to be more 

 alkaline than that of the submaxillary, to contain mucin, a dias- 

 tatic enzyme, and potassium sulphocyanate. 



The secretion of the mucous glands of the human mouth has 

 never been obtained pure, or in quantity sufficient to analyze. It 

 is a tenacious and viscid secretion and alkaline in reaction. 



Mixed saliva i. e., the saliva as found in the mouth the 

 product of all the salivary glands, is a clear fluid, viscid in con- 

 sistency, with a specific gravity between 1.002 and 1.008, alkaline 

 in reaction, and containing from 5 to 10 parts per 1000 of total 

 solids. It is secreted to the amount of between 300 and 1500 

 grams daily. Moore states that when it is acid this reaction is 

 commonly due to fermentation of particles of food in the mouth. 

 Many authorities state that it contains sodium carbonate, but 

 Chittenden and Richards make the following statement : " Human 

 mixed saliva contains normally no sodium carbonate whatever; 

 the alkalinity indicated by litmus, lacmoid, etc., is due to hy- 

 drogen alkali phosphates, with possibly some alkali bicarbonate. 

 Mixed saliva invariably acts acid to phenolphthalein. 



" The alkalinity of mixed saliva, as indicated by lacmoid, is 

 greater before breakfast than after the morning meal ; a conclusion 

 which stands in direct opposition to the statement frequently made 

 that ' the alkalinity (of mixed saliva) is least when fasting, as in 

 the morning before breakfast, and reaches its maximum with the 

 height of secretion during or immediately after eating/ " 



When saliva is examined under the microscope there are seen 

 epithelial scales from the mucous membrane of the mouth, and 

 leukocytes, probably from the tonsils and elsewhere, described 

 usually as salivary corpuscles. Bacteria and portions of food are 

 commonly found in saliva, but they are not constituent parts, but 

 rather impurities. 



Examined chemically the saliva is found to contain the enzyme 

 ptyalin, mucin, and traces of proteid, probably of the nature of a 

 globulin, but too little in amount to be quantitatively determined. 

 It contains also, though not invariably, potassium sulphocyanate, 

 which is regarded as a product of proteid metabolism ; but with 

 our present knowledge the physiologic value of this constituent is 

 still undetermined. 



The inorganic constituents of saliva are sodium chlorid, cai- 



