SKULL OF THE OX AS A WHOLE 



125 



the apex of the petrous, where it is joined by the condyloid canal. The foramen 

 lacerum is divided into two parts (For. lacerum anterius et posterius). 



The nasal cavity is incompletely divided by the septum, which does not reach 

 the floor posteriorly. The floor is relatively long, and is more concave from side to 

 side than in the horse. In the dry skull it has a large oval opening into the palatine 

 sinus, which is closed during life by mucous membrane. The middle meatus is 

 divided behind into upper and lower branches by the great ethmoturbinal. The 

 posterior nares are narrow and oblique. 



Fig. 97.^ — Skull of Ox, Dorsal View. 

 The outer plate of bone has been removed to show the sinuses, a, Frontal sinus; a', cranial plate of 

 frontal bone ; a", anterior part of frontal sinus, which is separated from remainder by a septum (6); c, c', 

 communications between frontal sinus and nasal cavity; d, supraorbital foramen; e, supraorbital canal; /, cavity 

 of superior turbinal bone, and g, its opening into the nasal cavity; /;, lacrimal sinus, i, its communication 

 with the maxillary sinus; k, maxillary sinus; Z, orbit; 1, frontal bone; i', processus cornu; 2, nasal bone; S, 

 premaxilla (nasal process); 4, maxilla; 5, lacrimal bone; 6, malar bone; 7, dotted line indicating course of naso- 

 lacrimal duct. (After Ellenberger, in Leisering's Atlas.) 



The frontal sinus is very large. It involves almost all of the frontal bone and 

 a large part of the posterior wall of the cranium. It also extends for a variable dis- 

 tance into the horn processes when these are present. A complete median septum 

 separates the right and left sinuses. The anterior limit is indicated by a transverse 

 plane through the middle of the orbits. It extends externally to the crest which 

 limits the temporal fossa above, and into the root of the supraorbital process. At 

 the highest part of the cranial cavity and at the tuberosity on the posterior surface 



