278 SPLANCHNOLOGY. 



borders. Its superior border is attached to the palatine arch, 

 and is continuous with the hard palate, whence the velum passes 

 downwards and backwards. The lateral borders are united to 

 the line of demarcation between the cavity of the mouth and that 

 of the pharynx. The inferior border is concave and free, resting 

 upon, and closely embracing the base of the epiglottis. From 

 the extremities of this border, two very thin prolongations run 

 along the lateral walls of the pharynx as far as the beginning of 

 the oesophagus; these are the 'posterior pillars of the fauces. 

 Between the free border of the velum pendulum palati and base 

 of the epiglottis is the posterior opening of the mouth, called the 

 isthmus faucium, which in the horse, from the extreme development 

 of the soft palate, is constantly shut, except during the passage of 

 food or water. It is owing to the great size of the velum that a 

 horse is unable to breathe through his mouth. The anterior 

 surface of the velum forms the posterior boundary of the mouth, 

 is marked by longitudinal folds and transverse lines, and studded 

 with the mouthlets of numerous submucous glands. This surface 

 is united laterally to the base of the tongue by large mucous 

 columns, the posterior pillars of the tongue, or anterior pillars 

 of the fauces. Behind these are two lateral triangular spaces, the 

 tonsilar spaces, which take the place of the tonsils or amygdalce, 

 these being absent in the horse; numerous gland ducts open in 

 these spaces. The posterior surface of the soft palate is convex, 

 and forms the anterior wall of the pharynx ; it presents three 

 very small longitudinal ridges. 



MUSCLES OF THE SOFT PALATE. 

 A strong layer of aponeurosis or fibrous tissue, the staphyline 

 aponeurosis, forms as it were the foundation of the soft palate, 

 being attached above to the palatine arch. The following muscles 

 control the soft palate : — 



Teusor palati. I Pharyngo-staphylinus. 



Levator palati. | Palato-staphylinus. 



Palato-glossus. 



TENSOR PALATL 



{Peristaphylinus Externus.) 



(Fig. 90. i.) 



A long slender muscle with tendinous extremities, running 

 longitudinally between the levator palati and the pterygoidei. It 



