236 DIGESTIVE SYSTEM. 



side ; but this contracts them, and occasionally projects them in 

 such a manner, that the horse can exert with them a prehensile 

 power, which is most remarkably evinced at the time that he is 

 picking up grain from a plain surface ; indeed, the act of nibbling 

 our hands with his lips demonstrates this facidty, and also the 

 force with which he can employ it. The lips are lined by the 

 same membrane that lines other parts of the cavity of the mouth. 

 Beneath it are seated numerous mucous follicles that elevate it 

 everywhere into little papilla, which are perforated by the 

 mouths of these follicular glands, as may be readily seen with the 

 naked eye by everting either the superior or the inferior lip. The 

 skin covering the lips is extremely thin, and possesses consider- 

 able vascularity and sensibility. To the tenuity of it, and to the 

 shortness and scantiness of their pilous covering, is to be ascribed 

 the superior sensitive faculty of these parts. 



Cheeks. 



The cheeks are constituted substantially of the masseter and 

 buccinator muscles, covered by the skin upon the outside, and the 

 buccal membrane upon the inside. Their internal or membranous 

 surface is studded with scattered mucous follicles, whose excretory 

 orifices may be seen by everting the part. 



G 



urns. 



The gums consist of dense, compact, prominent, polished 

 masses, of the nature of periosteum, adhering so closely and te- 

 naciously to the teeth and the sides of their sockets, that it ren- 

 ders the one inseparable from the other but by extraordinary 

 mechanical force. Like other parts of the cavity of the mouth, 

 they rec^iive a covering from the buccal membrane. 



Palate. 



Two distinct parts are included under this head ; the/?cr/'c?and 

 the soft, palate. The hard palate is constituted of the palatine 

 processes of the superior and anterior maxillary bones ; and of a 

 firm, dense, periosteum -like substance, the vaulted, inward part 

 of which is elevated into several semicircular ridges, vulgarly 

 called the bars. The fibies of this substance, which possess 

 great tenacity, are inserted into the pores of the bone in every 

 part, but are most numerous and dense along the palatine suture : 

 the interstices are filled up by a dense cellular tissue, through 

 the substance of which are dispersed the ramifications of the 

 j)alatine vessels and nerves. 



THB SOFT PALATE, sometimes called the velum palati, is 



