HEAD AND NECK OF THE HORSE 77 



layers: — (1) The relatively thick oral mucous membrane continuous 

 with that of the hard palate; (2) a layer of palatine glands; (3) an 

 aponeurotic and muscular layer ; and (4) the pharyngeal mucous 

 membrane continuous with that of the nasal cavity. 



Disseclioti. — Dissect the mucous ineiubiane from the jDharyngeal 

 surface of the soft palate. The muscular and aponeurotic layer contains 

 the origin of the palato-pliaryngeal muscle (already dissected in connection 

 with the wall of the pharynx), the termination of the levator and tensor 

 muscles of the palate, and the muscle of the uvula (m. uvulte). It is 

 convenient to dissect the whole length of the tensor and levator muscles 

 at this stage. 



M. UVUL^. — The muscle of the uvula^ is often described as being 

 unpaired, but probably the best way to regard it is as a pair of muscles 

 (right and left) blended in the middle line of the soft palate. It has a 

 wide aponeurotic origin from the free border of the palatine bone, and 

 ends near the free border of the soft palate. 



M. TENSOR VELI PALATINI.— The tensor of the soft palate lies along the 

 lateral surface of the auditory tube. Arising from the muscular process 

 of the temporal bone, the lateral lamina of the cartilage of the auditory 

 tube and the pterygoid bone, the muscle ends in a narrow, flattened 

 tendon that bends round the hamulus of the pterygoid bone to end 

 in the general aponeurosis of the soft palate. A small synovial bursa 

 facilitates the play of the tendon round the pterygoid hamulus. 



M. LEVATOR VELI PALATINI. — The levator of the soft palate arises 

 from the muscular process of the temporal bone and the lateral lamina 

 of the cartilage of the auditory tube in common with the tensor, medial 

 to which it lies. The two levator muscles (right and left) enter the 

 substance of the soft palate close together. 



Dissection. — Reflect the muscular and aponeurotic layer of the soft 

 palate so as to expose the glands. 



The greyish-yellow palatine glands (gland ul;v palatines) form a 

 layer of 1 cm. or more in thickness. It is important to note that their 

 ducts open only on the ventral or oral surface of the soft palate ; that 

 is, the mucous glandular secretion is poured out on that surface with 

 which the food comes into contact during its passage from the moutli to 

 the pharynx. 



Dissection.-^^l&ke. a longitudinal incision through the most lateral 

 part of what still remains of tlie soft palate. 



The MOUTH (Cavum oris). — The cavity of the mouth is the initial 

 part of the alimentary tract and extends from the lips to the isthmus 



1 Uvula [L.], dim. of uva, a grape. 



