154 ANATOMY OF THE RABBIT. 
being formed by the nasal bone. The palatine process extends 
backward on the medial side of the bone, closely applied on the 
palatal surface to its fellow of the opposite side, and forms in this 
way a medial boundary for the incisive foramen. Its dorsal 
surface, in conjunction with that of the corresponding process of 
the other side, bears a broad palatine groove (sulcus palatinus), 
lodging a portion of the cartilage of the vomeronasal organ and 
nasopalatine duct. The frontal process (processus frontalis) 
is a thin bony splint, extending backward between the nasal and 
maxillary bones, and terminating between the former and the 
maxillary process of the frontal. 
14. THE ZYGOMATIC BONE. 
The zygomatic bone (os zygomaticum) is a separate element 
only in very young animals. In the adult it is fused anteriorly 
with the zygomatic process of the maxilla, the position of the 
original suture being roughly identifiable as the point where the free 
horizontal portion of the zygomatic arch arises from the transverse 
zygomatic process. It forms an almost sagittal plate of bone 
bridging the orbit and serving for the attachment of the masseter 
muscle of the mandible. Its dorsal margin forms posteriorly 
a smooth, horizontal articulation with the zygomatic process of the 
squamosal, the end of the bone projecting considerably behind the 
articulation. 
15. THE NASAL BONE. 
The nasal bone (os nasale) is a thin, elongated bone forming 
the roof of the nasal fossa, and, in conjunction with its fellow of the 
opposite side, the dorsal boundary of the piriform aperture. It is 
loosely articulated with the maxilla and with the bone of the 
opposite side by smooth (harmonic) sutures. The medial margin 
is supported by the dorsal edge of the nasal septum. The internal 
surface bears the nasoturbinal scroll. 
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