HEAD AND NECK OF THE HORSE 



151 



the short naso-palatine duct (ductus nasopalatinus) that, in the 

 majority of domestic mammals, opens into the mouth at the side of the 

 incisor papilla. In the horse, however, the duct ends blindly in the 

 cartilage that occludes the palatine fissure. 



N. buccalis ventralis. 



N. buccalis ddrsalis. 



Concho-frontal sinus. 



Maxillary sinus (posterior part). 

 / 

 Maxillary sinus (anterior part). 



Infraorbital canal. 



N. infraorbitalis. 



M. levator labii superioris 



proprius. 

 ^ M. nasolabialis. 



M. masseter 



A. facialis. I M. buccinator. 

 Parotid duct. 



Fig. 66. — Lateral aspect of the maxillary paranasal sinus. 



Into the nasal end of the naso-palatine duct opens the tubular 

 vomero-nasal organ (organon vomeronasale), which, enclosed in the 

 vomxero-nasal cartilage (cartilago vomeronasalis) at the base of the 

 nasal septum, extends backwards as far as the level of the third or 

 fourth cheek-tooth. 



The paranasal sinuses (Sinus paranasales). — The paranasal sinuses, 

 or air sinuses of the skull, are irregular cavities produced by the 



