276 SPLANCHNOLOGY. 



with accessories, the preparatory with teeth and salivary glands^ 

 and the essential organs with the liver, pancreas, spleen, &c. 



We will describe the parts of the alimentary canal in the order 

 above given — the order in which the food traverses them. 



THE MOUTH. 



The mouth is an irregularly oval cavity at the commencement 

 of the alimentary canal, containing the organs of taste and the 

 instruments of mastication ; it is situated between the jaws, its 

 long diameter following that of the head. It is pierced by two 

 openings ; the anterior for the introduction of food, and the 

 posterior, through which the latter passes into the pharynx. It 

 is bounded in front by the lips and their aperture, the fissura 

 oris, and laterally by the cheeks ; the roof is formed by the hard 

 palate ; its floor is occupied by the tongue, while the posterior 

 boundary is the veluTYi pendulum palati, or soft palate, a mem- 

 branous partition separating it from the pharynx. The mucous 

 membrane is pale, roseate, continuous with the skin at the lips, 

 and covering the whole free surface of the mouth and its contents, 

 excepting the teeth. 



THE LIPS. 



The labia, or lips, superior and inferior, are movable fleshjr 

 curtains surrounding the anterior opening, and united laterally by 

 a commissure. They consist of skin and mucous membrane, 

 Avhich enclose muscles, vessels, nerves, areolar tissue, fat, and 

 certain labial glands situated between the mucous membrane and 

 muscle. The mucous surface of each lip is bridled mesially to 

 the gum by a doubling of the membrane, constituting the 

 fra^num labii superioris and inferioris. The arterie-^, and veins 

 of the lips are the palato-labials and the superior and inferior 

 coronaries. The nerves come from the fifth and seventh cranial 

 pair, the first supplying the sensory, or nerves of feeling, which 

 are well developed in the lips of the horse, since these are organs 

 of touch as well as of prehension. 



THE CHEEKS. 



The buccal, or cheeks, are two musculo-membranous walls, 

 -which close the mouth laterally ; they are continuous with the 



