280 SKELETON OF THE EABBIT 



■wards in front of the pre-sphenoid, separating 

 the right and left olfactory cavities from each 

 other. 



Its upper and posterior border is ossified 

 and expanded laterally into the cribriform 

 plate, which is placed obliquely across the 

 anterior end of the cranial cavity, in the plane 

 of the base of the skull, and is perforated by 

 a number of holes through which the olfactory 

 nerves pass from the brain to the nose. 



2. The sense-capsules. Each of the organs of special sense 

 has, as in the dog-fish, a protecting investment of 

 cartilage or strong connective tissue. In the case of 

 the olfactory and auditory organs these capsules are 

 closely connected with the cranium, and are more or 

 less extensively ossified. Membrane-bones are also 

 developed in immediate relation with the sense- 

 capsules, and may conveniently be considered with 

 them. 



a Bones in relation with the olfactory capsules. , The 



olfactory capsules are of very large size in the 

 rabbit, and occupy a great part of the facial por- 

 tion of the skull. They are so closely connected 

 with the ethmoidal region and with the upper 

 aw, that certain of the bones may be referred, 

 with equal propriety, to either of these divisions, 

 i. The nasals are a pair of elongated membrane- 

 bones, forming the roof of the nasal cavities. 

 They unite suturally with the frontals behind, 

 and with each other in the median plane, 

 i. The ethmo-turbinals are intricately folded laminse 

 of bone, fused to the lower surface of the cri- 

 briform plate of the ethmoid, and occupying 

 the upper and posterior part of each nasal 

 cavity, 

 iii. The maxillo-turbinals are a pair of somewhat 

 similar, but more delicate and more complex 



