BONES OF THE FACE 137 



frontal sinus. In the polled breeds these processes are absent, the skull is narrower 

 here, and the frontal eminence more pronounced (Fig. 139). The supraorbital proc- 

 ess is situated about half-way between the anterior and posterior margins; it is 

 short and joins the frontal process of the malar bone. The supraorbital foramen 

 (often double) is situated about an inch medially from the root of the process; it 

 is the external orifice of the supraorbital canal (Canalis supraorbitalis), which passes 

 downward and forward to the orbit. The foramen is in the course of the supra- 

 orbital groove (Sulcus supraorbitalis), which marks the course of the frontal vein. 

 The anterior ends of the naso-frontal parts form a notch which receives the nasal 

 bones, and sutural (or Wormian) bones are often found at this junction (naso- 

 frontal suture). The orbital part is extensive; it is perforated behind by the or- 

 bital opening of the supraorbital canal, and below by the ethmoidal foramen. It 

 does not articulate with the palatine bone, from which it is separated by the or- 

 bital wing of the sphenoid. The temporal part is also more extensive than in the 

 horse. The frontal sinus is very extensive, being continued into the parietals and 

 occipital, and the horn processes when present. 



The squamous and petrous parts of the temporal bone fuse early— in fact 

 union is nearly complete at birth. The squamous part is relatively small. Its 

 lateral surface is divided into two parts by the prominent temporal crest, which is 

 continuous with the parietal crest above and turns forward below, ending at a 

 tubercle above the external acoustic meatus. The part behind the crest faces 

 backward, and is partly free, partly united with the occipital. The area in front 

 of the crest is concave and enters into the formation of the temporal fossa; it is 

 perforated by foramina which communicate with the temporal canal. The zygo- 

 matic process is much shorter and weaker than in the horse, and articulates with the 

 malar only. The condyle is convex in both directions. The postglenoid process 

 is less prominent, and behind it is the chief external opening of the temporal canal. 

 The cerebral surface is almost completely overlapped by the parietal and sphenoid. 

 The petrous part is small, but the tympanic part is extensive. The external 

 acoustic meatus is smaller than in the horse and is directed laterally. From it a 

 plate projects downward and helps to inclose the deep depression in which the hyoid 

 process is placed. Behind this plate is the stylo-mastoid foramen. The muscular 

 process is large and often bifid at its free end. The bulla ossea is large and later- 

 ally compressed. It is separated from the occipital bone by a narrow opening 

 which is equivalent to part of the foramen lacerum of the horse. The temporal 

 canal is formed entirely in the temporal bone. The facial canal, on the other 

 hand, is bounded partly by the occipital bone. 



Bones of the Face 



The maxilla is shorter but broader and relatively higher than in the horse. 

 Its lateral surface bears the rough facial tuberosity (Tuber faciale), placed above the 

 third and fourth cheek teeth; a rough line which extends backward from it to the 

 upper part of the malar bone may be regarded as the facial crest. The infraorbital 

 foramen — often double — is situated above the first cheek tooth. The tuber maxil- 

 lare is small, laterally compressed, and usually bears a small pointed process (Pro- 

 cessus pterygoideus). The zygomatic process is very small. The interalveokr 

 border is concave, and there is no alveolus for a canine tooth. The palatine 

 process is wider, but somewhat shorter than in the horse. It incloses a large 

 air-space, which is continuous behind with a like cavity in the horizontal part of 

 the palate bone, forming the palatine sinus (Sinus palatinus). This communi- 

 cates Jaterally (over the infraorbital canal) with the maxillary sinus; in the 

 macerated skull it communicates with the nasal cavity by a large oval opening, 

 which is closed by mucous membrane in the fresh state. A median septum sepa- 



