174 ANATOMY OF THE RABBIT 



also the entire olfactory region of the primary skull, including the 

 nasal fossae and associated turbinal bones. The upper jaw — the 

 maxilla of the human skull— is formed of two primary, and, in the 

 rabbit, separate, elements, the maxilla and premaxilla. They 

 together form the greater portion of the facial region — in the adult 

 condition also a large portion of the lateral walls of the nasal fossae 

 — and bear in a ventrolateral position low alveolar processes 

 (processus alveolares) for the sockets or alveoli of the incisor and 

 cheek-teeth. The maxilla bears the anterior root of the zygomatic 

 arch, the latter being formed partly by a short zygomatic process 

 arising from the lateral surface of the maxilla, by the zygomatic 

 or malar bone, which is fused with it, and by the corresponding 

 zygomatic process of the squamosal bone, constituting the posterior 

 root. The anterior root of the zygomatic arch is perforated by a 

 deep narrow infraorbital canal (canalis infraorbitalis), which opens 

 on the facial surface by a vertical slit-like aperture, the infraorbital 

 foramen. It serves for the transmission of the infraorbital vessels 

 and nerves from the orbit to the face. 



The ventral portion of the maxilla is associated with the pala- 

 tine bone to form the hard palate (palatum durum). This structure 

 is represented chiefly by a bony palatine bridge connecting the 

 two sides of the skull between the more anterior cheek-teeth. It 

 forms a portion of the roof of the oral cavity and a portion of the 

 floor of the nasal cavity. Immediately in front of it, the palatal 

 surface is perforated by a pair of large incisive foramina (foramina 

 incisiva), which are broadly open to the nasal fossae. 



A considerable portion of the anterior and dorsal wall of the 

 orbit is formed by the facial complex. Dorsally, the roofing element 

 of this region, the frontal bone, bears a curved lateral projection, 

 the supraorbital process (processus supraorbitalis), which over- 

 hangs the orbit. Its narrower base expands into anterior and 

 posterior tips, which lie parallel to the adjacent portion of the skull, 

 and enclose with the latter corresponding anterior and posterior 

 supraorbital incisures. Ligaments convert these incisures into 

 foramina, the anterior for the passage from the orbit of the frontal 

 nerve and the frontal artery, the posterior for the emergence of the 

 lacrimal nerve and the lacrimal artery. The anterior wall of the 

 orbit is formed in part by a loosely articulated element, the lac- 



