the inside of the mouth. The other part of the 

 saliva contains, besides the Usual salts of the se- 

 rum, a peculiar matter, remarkable in this respect, 

 that it cannot be coagulated either by boiling, or 

 by the tanning principle, or the subacetate of lead. 

 With water it resolves itself into a liquid frothy 

 solution, although it should be observed, that the 

 saliva derives its property of forming threads 

 only from the mucus, which is mixed with it. 

 The viscidity of the saliva has been considered 

 only as intended to mix small particles of air with 

 the substance, which is chewed. This, however, 

 I consider as a mistake. It may probably have 

 the mechanic purpose of preparing a slippery 

 and coherent mass from the chewed food, in or- 

 der to promote its being more easily swallowed ; 

 but it is not at all decided how far it may 

 contribute to the solution of the food. When 

 part of the mucus of the saliva remains on the 

 teeth, it thickens, gets coloured, and forms what 

 is called tartar; and I have found this to be of a 

 two-fold kind: when just settled it is clearly 

 nothing else than the darkened mucus ; but during 

 the destruction of the mucus we insensibly per- 

 ceive phosphate of lime on the enamel of the 

 tooth, which sometimes is increased to a crust of 



