HEAD AND NECK OF THK HORSE 



155 



coronal suture). The anterior limit reaches a transverse plane midway 

 between the edge of the orbit and the end of the facial crest. Medially 

 the two concho-frontal sinuses are only separated by a thiunish plate of 

 bone. Laterally the sinus extends to within a short distance of the 

 margin of the orbit, and, in front of the orbit, is separated from the 

 maxillary sinus by little more than the width of the naso-lachrymal 

 bony canal. 



Ethmoidal labyrinth. 



Concho-frontal sinus. 



Naso-lachrymal 

 duct. 



N. infraorbitalis.- 



Maxillary sinus 



Nasal cavity.- - 



.Nasal septum. 



_Nasal mucous 

 membrane. 

 -V. reflexa. 



^> Nn. buccales. 



--A. palatina major. 



Soft palate. 



Tongue. 



Fig. 69. — Transverse section of the face in tlie same plane (D in Fig. 1) as Fig. 68, but looking 

 backward. The section strikes the communication between the concho-trontal 

 and maxillary sinuses. 



The sinus must be opened by gradually snipping away the frontal 

 bone. In doing this, it should be noted that a curved partition of bone 

 extends from the median septum towards the ethmoidal labyrinth, and 

 imperfectly divides the sinus into anterior and posterior parts. It 

 should also be observed that the most anterior part of the cavity is 

 contained in the dorsal turbinated bone, the thin plate of which alone 

 serves to separate it from the nasal cavity. 



The concho-frontal communicates with the maxillary sinus by a 

 large, oval opening between the labyrinth of the ethmoid and the bony 

 naso-lachrymal canal. 



The spJieno-'palaiine sinus (.sinus sphenopalatinus) is the smallest 

 of the cavities of the skull, and occurs in the body of the sphenoid bone 



