FUNCTIONS OF THE SALIVA. 179 



starch, in the human subject at least, must exist in the pure 

 secretion from the various glands, as well as in the mixed 

 saliva. It has been isolated and studied by Mialhe, under 

 the name of animal disastase. Its properties and its action 

 on starch have already been noted in treating of the compo- 

 sition of the mixed saliva. 



In treating of the various fluids which are combined to 

 form the mixed saliva, their mechanical functions have neces- 

 sarily been touched upon. To sum up this subject, however, it 

 may be stated that the fluids of the mouth and pharynx have 

 quite as important an office in preparing the food for deglu- 

 tition and for the action of the juices in the stomach, as in the 

 digestion of starch. Indeed, the former is probably the more 

 important function in man and the herbivora. It is a. matter 

 of common experience that the rapid deglutition of very dry 

 articles is impossible; and the experiments of Bernard and 

 others on horses furnish very striking illustrations of the im- 

 portance of the saliva as a purely mechanical agent. In 

 the human subject, though mastication and insalivation 

 are by no means so complete as in some of the lower ani- 

 mals, the quantity of saliva absorbed by the various articles 

 of food is enormous. The observations of Dalton, which 

 have been already referred to in treating of the entire quan- 

 tity of saliva, show that white bread absorbs in the mouth 

 fifty -five per cent., and cooked meat, forty-eight per cent, of 

 its original weight. 1 It seems impossible that the fluid 

 thus incorporated with the alimentary principles should not 

 have an important influence on the changes which take place 

 in the stomach, though it must be confessed that our infor- 

 mation on this point is very meagre, except as regards the 

 digestion of starch. 



It is undoubtedly the abundant secretion of the parotid 

 glands which becomes most completely incorporated with 

 the food during mastication, and serves to unite the dry par- 

 ticles into a single coherent mass. In an experiment on a 

 1 Op. tit., p. 128. 



