200 DIGESTION MASTICATION, INSALIVATION, DEGLUTITION. 



COMPOSITION OF HUMAN SALIVA. 



Water 995-16 



Epithelium 1-62 



Soluble organic matter 1-34 



Potassium sulphocyanide 0'06 



Sodium, calcium and magnesium phosphates 0*98 



Potassium chloride ) 

 Sodium chloride } ' 



1,000-00 



The organic matter of the mixed saliva, called by Berzelius, ptyaline, on 

 the addition of an excess of absolute alcohol, is coagulated in the form of 

 whitish flakes which may be readily separated by filtration. This substance 

 has been studied by Mialhe and is described by him under the name of 

 animal diastase. This author regards it as the active principle of the saliva. 

 It has no direct influence upon the nitrogenized alimentary matters, but 

 when brought in contact with hydrated starch, readily transforms it, first into 

 dextrine and afterward into glucose. According to Mialhe, the energy of 

 this action is such that one part is sufficient to effect the transformation of 

 more than two thousand parts of starch. 



The presence of a certain quantity of potassium sulphocyanide in the 

 mixed saliva can be demonstrated by the addition of a per-salt of iron. That 

 this is a constant and normal ingredient of the human saliva, can not be 

 doubted. 



Very little need be said concerning the other inorganic constituents of 

 saliva, except that they are of such a nature as almost invariably to render 

 the fluid distinctly alkaline. They exist in small proportion and do not 

 appear to be connected in any way with the action of the saliva as a digest- 

 ive fluid. 



USES OF THE SALIVA. 



In 1831, Leuchs discovered that hydrated starch, mixed with fresh saliva 

 and warmed, became liquid and was converted into sugar. This fact has 

 since been repeatedly confirmed ; and it is now a matter of common observa- 

 tion that hydrated starch or unleavened bread, taken into the mouth, almost 

 instantly loses the property of striking a blue color with iodine and responds 

 to the ordinary tests for sugar. Of the rapidity of this action any one can 

 easily convince himself by the simple experiment of taking a little cooked 

 starch into the mouth, mixing it well with the saliva, and testing in the ordi- 

 nary way for sugar. This can hardly be done so rapidly that the reaction 

 is not manifested, and the presence of sugar is also indicated by the taste. 

 Although the human mixed saliva will finally exert the same action on un- 

 cooked starch, the transformation takes place much more slowly. 



It has been shown that all the varieties of human saliva have the same 

 effect on starch as the mixed fluids of the mouth. Dalton found no differ- 

 ence between the pure parotid saliva and the mixed saliva of the human 

 subject, as regards the power of transforming starch into sugar. Bernard 



