1208 THE ANATOMY OF THE HORSE. 



upper lip. Iii passing in to join its fellow at the incisor foramen the 

 palato-labial artery runs under a small flexible bar of cartilage, which 

 is fixed to the bone by its upper extremity, while its lower extremity is 

 free. Where the artery curves inwards it detaches a branch that 

 passes downwards to be distributed in the palate below the level of the 

 incisor foramen. 



Palatine Veins. Over the whole extent of the hard palate there 

 exists a rich network of veins in the sub-mucous connective-tissue. 

 This network is drained by a large vein which accompanies the 

 palato-labial artery as far as the lower orifice of the palatine canal. 

 There it parts company with the artery, and passes along the staphy- 

 line groove, with the staphyline artery and nerve. It joins the 

 alveolar vein. The variable thickness of the palate depends princi- 

 pally on the amount of blood in these veins, this being greatest in 

 the young animal. 



The Palatine Nerve is a branch of the superior maxillary division 

 of the 5th. It emerges from the palatine canal, along with the artery, 

 around which its branches interlace. It is the sensory nerve to the 

 .hard palate. 



THE SOFT PALATE, OR VELUM PENDULUM PALATI. 



This is an oblique valvular curtain placed on the limit of the oral and 

 pharyngeal cavities. The oral surface of the curtain looks downwards 

 and backwards, and is covered by mucous membrane continuous with that 

 of the hard palate. The pharyngeal surface has the opposite direction, 

 and its mucous covering is continuous with that of the nasal chambers. 

 The anterior edge is fixed at the posterior margin of the hard palate. 

 The lateral edges are attached on the limits of the mouth and pharynx. 

 The posterior edge is free, and extends across the root of the tongue, in 

 front of the epiglottis. The mucous membrane in passing between the 

 soft palate and the root of the tongue is raised on each side into 

 a fold, and two similar but less prominent ridges of mucous membrane 

 extend from the soft palate to the sides of the pharynx. These are 

 termed respectively the anterior and posterior pillars of the soft 

 palate, and between them is a space into which numerous mucous 

 glands open. Beneath the mucous membrane in this position there is a 

 quantity of lymphoid tissue, which represents the tonsil, although it 

 does not project above the surface as in most other animals. The soft 

 palate of the horse is remarkable for its large size — a fact which explains 

 the difficulty with which the horse can expire or eject regurgitated 

 matters through the mouth. 



The Isthmus of the Fauces. This is the aperture of communication 

 between the mouth and the pharynx. It is bounded in front and 

 laterally by the free edge of the soft palate, and by its anterior pillars. 



