DIFFERENT KINDS OF SALIVA. 43 



diversities, the number of digestive dilatations and their size correspond- 

 ing in some measure to the nature of the food. 



Three pairs of glands, the parotid, submaxillary, and sublingual, se- 

 crete saliva. Of these organs the parotid is the largest ; its Different kinds 

 secretion is delivered through the duct of Steno. The sub- of saliva - 

 maxillary duct is Wharton's, but the sublingual pours its fluid through 

 many small apertures near the frenum linguae Besides these proper sali- 

 vas, the lining membrane of the mouth yields a fluid, the buccal mucus. 



The parotid saliva is thin and watery, limpid and colorless, inodorous 

 and tasteless. Secreted during fasting or under the use of The parotid sa- 

 stimulating food, it is denser. It contains so large a quanti- liva - 

 ty of lime that, on exposure to the air, it becomes covered with an in- 

 crustation of the carbonate of that substance. It also contains sulpho- 

 cyanide of potassium. Its organic ingredient, if not albuminate of soda, 

 closely resembles that body. 



From the chemical constitution of the saliva of the parotids, the phys- 

 iological function of those glands, as aquiparous organs, is established. 

 They yield a certain quantity of watery juice, which, by reason of its 

 thinness or fluidity, is readily incorporated with the food by the teeth. 

 Parotid saliva appears to have no power of transmuting starch into sugar. 



The submaxillary saliva is also colorless and limpid, tasteless and in- 

 odorous. It contains no morphological elements. It is The submaxil- 

 lighter than the parotid, less alkaline, and contains less lime. lai r saliva. 

 For this reason, when exposed to the air, it does not become incrusted 

 with carbonate of that earth. It contains sulphocyanide of potassium. 

 It is so viscid and glutinous that it may be drawn into threads. From 

 this physical property it probably, facilitates deglutition by furnishing a 

 kind of anti-friction coating. 



The .sublingual saliva is thin and watery, containing, like the parotid, 

 but a small percentage of solid matter, and probably dis- The sublingual 

 charging a similar function. saliva. 



Besides the special salivary juices, the lining membrane of the mouth 

 pours forth a liquid the buccal mucus a thick and tena- The buccal mu- 

 cious substance, having many epithelial cells. It is alkaline cus - 

 in its reaction, does not coagulate on heating, its insoluble salts contain- 

 ing no carbonate of lime. It has been obtained for examination by tying 

 the ducts of Steno and Wharton, keeping the nostrils open and the head 

 inclined, so that, the animal being unable to swallow, the mucus flows out 

 of the mouth. 



The buccal mucus, if mixed with parotid saliva, does not appear to 



)ssess the power of turning starch into sugar, but, if mixed with the 

 submaxillary secretion, it accomplishes that transmutation with facility. 



The saliva, as obtained from the mouth, is therefore a mixture of the 



