136 Anatomy of the Rabbit. 



aperture of the facial canal (canalis facialis), which serves for the 

 transmission of the seventh cranial (facial) nerve. Immediately 

 behind and below this aperture is the opening of the internal 

 acoustic meatus (meatus acusticus internus) for the transmission 

 of the eighth cranial (acoustic) nerve. The two apertures tend to 

 be enclosed by a shallow bony ridge, largely formed by the pro- 

 jecting ledge described above, and resembling superficially the 

 complete common tube represented by the internal acoustic meatus 

 of the human skull. 



The facial portion of the skull is largely formed by the invest- 

 ing bones of the upper jaw, palate, and mandible, but it encloses 

 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 its lateral surface, 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 con- 

 necting 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 por- 

 tion 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. 



