LESSON 52.] 



NUTRITION IN THE MAMMALIA. 



183 



FIG. 288. 



have their external surface covered with a dense horny layer. This in- 

 crease in size continues to, and beyond 

 the centre, at which point they have 

 assumed very formidable dimensions 

 (a). Near the base of the tongue, the 

 circumvallate papillaB (c) are found ; 

 they are six in number. These are 

 only greatly enlarged fungiform papil- 

 lae, and the ditch by which they are 

 surrounded is filled with mucus- 

 crypts, or the mucus-follicles of Lei- 

 berkuhn, who first described them. 

 They are the external outlets of mu- 

 cus-tubes, mucus being abundantly 

 poured out to lubricate the upper sur- 

 face of the tongue. 



Beyond the Circumvallatae, are 

 other filiform papillae, but destitute of 

 a horny covering, their situation being 

 too remote to be effective as teeth; 

 they are covered with mucous crypts, 

 so well formed, that they possess a cal- 

 lous margin. From the peculiar cov- 

 ering of the filiform papillaB in the 

 Feline animals, it is probable that 

 they are not endowed with much sensibility as organs of taste, but 

 that this function is exercised by the fungiform papillae alone. 



797. The stomach is well formed (as regards its ultimate or 



FIG. 289. FIG. 290. 



Cat's tongue. 



Stomach of Cat' Ileum of Cat. 



microscopical character), as might be expected in a true carnivorous 

 animal, and a figure of the Cat's stomach is given (Fig. 289). 



798. Another remarkable modification of structure is met with 

 in the villi of the intestines, which in all these animals are singular- 



