SEC. 1. THE PROPERTIES OF THE DIGESTIVE JUICES. 



Saliva. 



Mixed saliva, as it appears in the mouth, is a thick, glairy, 

 generally frothy and turbid fluid. Under the microscope it is 

 seen to contain, besides the molecular debris of food (and fre- 

 quently cryptogamic spores), epithelium-scales, mucus-corpuscles 

 and granules, and the so-called saliva corpuscles. Its reaction in 

 a healthy subject is alkaline, especially when the secretion is 

 abundant. When the saliva is scanty, or when the subject suffers 

 from dyspepsia, the reaction of the mouth may be acid. Saliva 

 contains but little solid matter, on an average probably about 

 5 p. c., the specific gravity varying from T002 to T006. Of these 

 solids, rather less than half, about "2 p. c., are salts (including a 

 small quantity of potassium sulphocyariate). The organic bodies 

 which can be recognised in it are chiefly mucin, with small 

 quantities of globulin and serum-albumin. 



The chief purpose served by the saliva in digestion is to 

 moisten the food, and to assist in mastication and deglutition. In 

 some animals this is its only function. In other animals and in 

 man it has a specific solvent action on some of the food-stuffs. 

 Such minerals as are soluble in slightly alkaline fluids are dis- 

 solved by it. On fats it has no effect save that of producing a 

 very feeble emulsion. On proteids it has also no action. Its 

 characteristic property is that of converting starch into some form 

 of sugar. 



