174 DIGESTION. 



maxillary and sublingual glands, taken from the floor of the 

 mouth behind the inferior incisor and canine teeth. 1 



Very little need be said concerning the remaining inor- 

 ganic constituents of saliva, except that they are of such a 

 nature as almost invariably to render the fluid distinctly al- 

 kaline. They exist in small proportion, and do not appear 

 to be connected in any way with the functions of the saliva 

 ' as a digestive fluid. 



Functions of the Saliva. 



Physiologists are not entirely agreed concerning some 

 of the most important questions relating to the function 

 of the mixed saliva in digestion. Bernard, from observa- 

 tions on the lower animals, particularly on dogs, concludes 

 that the operation of the saliva is only mechanical ; while 

 others, in view of its property of rapidly transforming starch 

 into sugar, attribute to it an important chemical function. 

 The experiments on which the view of Bernard is based are 

 conclusive, so far as they go. He has shown that none of 

 the distinct varieties of saliva from the dog affect starch; 

 that a mixture of the fluids from the three salivary glands 

 is likewise inoperative ; and that the mixed saliva from the 

 mouth of the dog, containing the secretion of the mucous 

 glands of the mouth, converts starch into sugar with diffi- 

 culty. On the same page, however, he mentions the well- 

 known fact that the human mixed saliva changes starch into 

 sugar with great rapidity, 2 and that the same effect is pro- 

 duced by the unmixed parotid or submaxillary secretion. 3 

 In the dog, amylaceous principles taken by the mouth are 

 always found unaltered in the stomach, and are only trans- 

 formed into sugar in the small intestines ; but observations 

 have shown that this is not the case in the human subject. 

 These facts are a sufficient argument against the direct appli- 



1 LoNGET, op. cit., p. 162. 



2 BERNARD, Lemons de Physiologic Experimentale, Paris, 1856, p. 157 et seq. 



3 Ibid., p. 165. 



