CONSTITUTION OF SALIVA. 45 



saliva in the mixed secretion, nothing is known with certainty in the case 

 of man, but it is said that in horses the parotids furnish two thirds, the 

 submaxillaries one twentieth, and the sublinguals and mucous follicles 

 the rest. The secretion of the saliva goes on during sleep. 



To the active organic substance of the saliva the designation of ptya- 

 line has been given. It is regarded as a ferment, possessing in 

 several respects the properties of diastase, and hence has been t>a 

 called by Mialhe diastase salivaire. 



For the purpose of analysis, saliva should be obtained in a perfectly 

 fresh state, a condition not easily fulfilled, for it decomposes or changes 

 with rapidity. 



During these changes, alkaline carbonates, for example, are formed in 

 abundance, though they may have existed but to a small extent at first. 

 We have already seen that in this way parotid saliva, ex- Constitution of 

 posed to the air, yields crystals of carbonate of lime. The saliva - 

 following table is presented as offering an example of the average consti- 

 tution of mixed saliva. 



Constitution of the Saliva (Frerichs). 



Water 994.10 



Epithelium and mucus 2.13 



Fat 07 



Ptyaline and alcohol extract 1.41 



Sulphocyanide of potassium 10 



Fixed salts 2.19 



1000.00 



Of the fixed salts the chief are, the phosphates of soda, lime, and mag- 

 nesia, and the chlorides of sodium and potassium. The sulphocyanide 

 of potassium varies in amount considerably : it increases after meals, and 

 .especially after the use of condiments, salt, pepper, spices. Those arti- 

 cles wiuch contain sulphur, as mustard, garlic, radishes, increase its amount 

 in a very marked manner. 



Not only does the saliva, as derived from the different glands, present 

 differences of constitution ; it likewise differs in various ani- Modifications 

 mals, and in the same animal according to its age. This is of saliva - 

 observed even in the case of man. The saliva of an infant at the breast 

 possesses very little power of saccharizing starch, a transmutation which 

 that of the adult accomplishes with energy. 



The action of this secretion appears to be limited to starch, and certain 

 kinds of sugar, which first yield lactic and then butyric acid. It does not 

 exert any influence in transforming albuminous matter. 



The saliva discharges many functions. It is a necessary intermedium 

 in the sense of taste, for substances to be sapid must be more Functions of 

 or less soluble in this juice. If insoluble, they are tasteless. SJfliva - 

 It also moistens the interior of the mouth, and prevents the sensation of 



