48 THE SURGICAL ANATOMY OF THE HORSE 



pharynx and mouth, along the h'ne of demarcation between these two 

 chambers. 



The anterior face is covered by a continuation of the mucous 

 membrane of the hard palate, and this surface presents a number of 

 longitudinal and transverse folds or ridges. Upon close inspection there 

 are also here visible numerous minute orifices, which are the apertures 

 of the ducts of small glands which are placed in the sub-mucous layer. 



The posterior surface is covered by a continuation of the mucous 

 membrane of the nasal chamber, and at the posterior or free border of 

 the valve the mucous membranes enter into continuity with one another. 

 The mucous membrane of this surface is also thrown into ridges, but 

 these are more regular than are those of the anterior surface, and are 

 disposed in a longitudinal manner only. 



In structure the partition consists of: 



1. Two layers of mucous membrane ; 



2. A fibrous aponeurosis ; 



3. Muscles ; 



4. Vessels and nerves. 



1. The mucous membranes have already been described. 



2. The fibrous aponeurosis forms a powerful framework to the 



structure. It is attached anteriorly to the palatine bones, and 

 extends in a posterior and downward direction for about one- 

 half the length of the soft palate, where it becomes continuous 

 with the palato-pharyngeii muscles, the anterior attachment 

 to which it affords. 



3. Muscles. — The palato-pharyngeus muscle. This may be exposed by 



removing the mucous and glandular layers covering the 

 anterior face of the soft palate, when its continuity with the 

 fibrous aponeurosis will be made apparent. In the middle line 

 its fibres will be noticed to be intermixed with those of the 

 corresponding muscle of the opposite side. The muscle 

 extends upwards and backwards along the wall of the pharynx. 



