192 ANATOMY OF THE RABBIT 



the palatine bridge it is applied to the lateral surface of the palatine 

 bone, and is projected into the orbit as a broad ridge enclosing the 

 alveoli of the four posterior cheek-teeth. 



In the divided skull, the medial surface of the body of the maxilla 

 is found to be concealed by the ethmoturbinal. It contains a deep 

 longitudinal excavation, the maxillary sinus (sinus maxillaris), 

 widely open to the nasal fossa, but only seen to advantage when the 

 ethmoturbinal is removed. The lateral wall of the sinus corres- 

 ponds in position to the fenestrated area of the external surface. 

 It bears the chief part of the nasolacrimal canal. 



The alveolar process (processus alveolaris) is that portion of 

 the maxilla lodging the sockets of the cheek-teeth. In the rabbit 

 it is separated by the diastema, in which no teeth occur, from a 

 corresponding but imperfectly differentiated process of the pre- 

 maxilla. 



The palatine process (processus palatinus) extends toward the 

 median plane. It forms with its fellow of the opposite side about 

 two-thirds of the palatine bridge. 



The orbital process (processus orbitalis) is directed obliquely 

 toward the dorsal surface of the skull. In conjunction with the 

 lacrimal bone and the maxillary process of the frontal, it forms the 

 anterior orbital rim. It is continuous with the fenestrated portion 

 of the body, and its appearance as a process is largely due to its 

 solid character as compared with the perforated surface lying in 

 front of it. 



The zygomatic process (processus zygomaticus) forms the 

 anterior root of the zygomatic arch and, in the adult condition, is 

 fused with the anterior end of the zygomatic bone. Its ventral 

 angle bears a prominent masseteric spine for the attachment of 

 the ligament of the masseter muscle. 



The sphenoorbital process (processus sphenoorbitalis) lies on 

 the medial wall of the orbit, in a position opposite to the middle 

 portion of the ridge lodging the posterior cheek-teeth. It forms a 

 stout buttress, the tip of which is applied to the anteroventral 

 angle of the frontal bone. In this position it is visible from the 

 orbit, lying between the lacrimal bone and the ethmoidal process 

 of the orbitosphenoid. 



