82 Anatomy of thb Rabbit. 



root of the zygomatic arch, the latter being formed partly by a short 

 zygomatic process arising from its lateral surface, by the zygomatic 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 trans- 

 mission of the infraorbital vessels and nerves from the orbit to the face. 



The ventral portion of the maxilla is associated with the palatine 

 bone to form the hard palate (palatum durum) . This structure is repre- 

 sented 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 supra- 

 orbital process (processus supraorbitalis), which overhangs 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. The latter 

 are converted by ligament into foramina. The anterior wall of the orbit 

 is formed in part by a loosely articulated element, the lacrimal bone, 

 the lateral margin of which projects from the orbital rim as a blunt sub- 

 cutaneous process (processus subcutaneus). On the ventral side of its 

 base is the orbital opening of the nasolacrimal canal (canalis nasola- 

 crimalis), the bony enclosure of the nasolacrimal duct, which in the 

 natural condition leads from the corneal surface of the eye to the 

 anterior portion of the nasal fossa. A smaller projection forming the 

 ventral boundary of the nasolacrimal aperture is the hamulus lacri- 

 malis. Finally, in the ventral anterior angle of the orbit, the bases of 

 the three posterior cheek-teeth encroach to a considerable extent on 

 the orbital space. They are separated from the orbital wall by a deep 

 infraorbital groove (sulcus infraorbitalis), which leads forward into the 

 canal of the same name. They partly conceal two important apertures 

 of this region, the orbital opening of the pterygopalatine canal (canalis 

 pterygopalatine), leading to the palatal surface, and the sphenopalatine 

 foramen (foramen sphenopalatinum), leading to the nasal fossa. The 

 pterygopalatine canal opens ventrally in the palato-maxillary suture of 

 the hard palate by a rounded aperture, the greater palatine foramen 

 (foramen palatinum majus). 



The nasal cavity (cavum nasi) is enclosed by the maxilla and pre- 

 maxilla, with the assistance of paired roofing elements, the nasal bones. 

 Apart from the incisive foramina, which are closed in the natural con- 

 dition, the cavity is open at two points. Posteriorly it communicates 

 with the ventral surface of the skull by the choanae, which, in the rabbit, 

 are incompletely divided. Anteriorly it opens to the outside by the- 



