OF THE MOUTH. 281 



these gustatory points of nerves been excited, 

 than there is poured out into the mouth most 

 abundantly, by four distinct tubes, the saliva, that 

 fluid* which facilitates mastication, and directly 

 prepares the food for the action of the stomach. 

 And however well we might imagine such a sup- 

 ply of fluid to assist deglutition, this is not all that 

 is here done in preparation ; for whilst the morsel 

 is moved by tongue, and lips, and jaws, an appro- 

 priate fluid is collecting in what appear to be 

 mere irregularities in the back part of the throat, 

 but which are, in truth, so many receptacles that, 

 pointing towards the stomach, give out their con- 

 tents as the morsel passes. 



There is one curious circumstance which we 

 may notice before quitting this subject. Eating 

 seems always to be an act of the will, and at- 

 tended with gratification. It is well known that 

 the operation, or what is very nearly the same, 

 may go on within the stomach, without any out- 

 ward sign at least of pleasure. The gizzard (with 

 which we are most familiar in fowls, though it be, 

 in fact, found in the vegetable feeders of the dif- 

 ferent classes of animals) is correctly enough des- 



* We presume that the fluid is chiefly useful in mastication, as 

 the glands are large, and the fluid most abundant in animals that 

 chew the cud. In all, these glands are so disposed as to receive 

 gentle pressure from the motion of the jaw; so that, whilst their 

 vascular apparatus is excited by the sensibilities of the tongue, 

 the fluid is urged from the ducts by the pressure of the jaw and 

 muscles which move it. The fluid itself is neither acid nor alka- 

 line. 



25* 



