SALIVARY APPARATUS. 157 



out opposite to the incisor teeth, which are those 

 principally employed in this kind of mastication. 

 The saliva of the Armadillo is exceedingly viscid ; 

 probably for the purpose of lubricating the tongue 

 with a fluid capable of securing the adhesion of 

 ants, and other small insects : and in order that 

 it may be supplied in sufficient quantity, when 

 wanted, a receptacle, or bladder, is provided in the 

 course of the salivary duct of the submaxillary 

 gland, which opens at the extremity of the jaw.* 

 In Birds and Reptiles, which can hardly be said 

 to masticate their food, the salivary glands are 

 comparatively of small size ; the exceptions to this 

 rule occurring chiefly in those tribes which feed on 

 vegetables ; for in these the glands are more con- 

 siderable, t In Fishes there is no structure of this 

 kind provided, there being no mastication per- 

 formed ; and the same observation applies to the 

 Cetacea, and to the acephalous 3Iollusca. In the 

 cephalopodous and gasteropodous Mollusca, we 

 find a salivary apparatus of very considerable size : 

 Insects, and the Annelida,X also, generally present 

 us with organs which appear to perform a similar 

 office. 



The passage of the food along the throat is faci- 

 litated by the mucous secretions, which are poured 

 out from a multitude of glands interspersed over 

 the whole surface of the membrane lining that 

 passage. The Camel, which is formed for traversing 



* This structure was discovered by Professor Owen. 



f The large saUvary gland in the woodpecker, is seen at s, Fig. 

 271, page 119. 



t The bunch of filaments, seen at s, Fig. 260 (p. 92) are the 

 salivary organs of the leech. 



