PAROTID SALIVA. 429 



tication also exercises a strong influence upon the secretion of parotid 

 saliva, which is specially marked in certain herbivora. 



Human parotid saliva may be readily collected by the introduction 

 of a canula into STENSON'S duct. This saliva is thin, less alkaline than the 

 submaxillary saliva (the first drops are sometimes neutral or acid), 

 without special odor or, taste. It contains a little protein but no mucin, 

 which is to be expected from the construction of the gland. It also con- 

 tains a diastatic enzyme, which, however, is absent in many animals. 

 The quantity of solids varies between 5 and 16 p. m. The specific gravity 

 is 1.003-1.012. Potassium sulphocyanide seems to be present, though 

 it is not a constant constituent. KULZ 1 found a maximum of 1.46 per 

 cent oxygen, 3.8 per cent nitrogen, and in all 66.7 per cent carbon dioxide 

 in human parotid saliva. The quantity of firmly combined carbon dioxide 

 was 62 per cent. 



The quantity and composition of the saliva from the mucin glands 

 as well as from the albuminous glands, as PAWLOW'S 2 school has shown, 

 is greatly dependent in dogs upon the psychical excitement, but also upon 

 the kind of substances introduced into the mouth, and an adaptation 

 of the glands for various mechanical and chemical irritants is found 

 to occur. Under the influence of hard and dry food the glands secrete 

 an abundance of saliva, while with food rich in water the secretion 

 is considerably less and accommodates itself to the quantity of water 

 in the food. Milk is an exception to this rule, as it causes a more abundant 

 secretion of saliva than meat. This is of importance in digestion of milk,, 

 as in the stomach the mixture of milk and saliva does not coagulate to 

 a compact mass, but separates in a finely divided, readily digestible con- 

 dition. By the action of strong chemical bodies the saliva is secreted in 

 proportion to the strength of the irritant. According to POPIELSKI 3 

 this is true only for irritants of medium strength, as after stronger irrita- 

 tion, for example with capsicin solution, the quantity of saliva decreases 

 with the increase in the amount of irritant. The irritating substance 

 is diluted by the saliva and the mouth is washed out at the same time 

 (PAWLOW). The partaking of acid produces, according to PAWLOW, a 

 thin saliva, poor in mucin, in quantities sufficient to neutralize the acid. 

 This claim does not agree with the observations of POPIELSKI, who found 

 that isomolecular acid solutions produced the secretion of the same 

 amount of saliva, and that on using isopercentage acids the quantity of 

 saliva was in inverse proportion to the molecular weight of the acid. 



1 Zeitschr. f. Biologic, 23. 



2 Arch, internet, de Physiol., 1, 1904. See also Boos, Maly's Jahresber., 36, 

 390, and Neilson and Terry, Amer. Journ. of Physiol., 15, as well as the work of Mendel 

 and Underhill, Journ. of biol. Chem., 3. 



3 Pfliiger's Arch., 127. 



