66 ELEMENTARY BIOLOGY. [CHAP. 



on the side which has been dissected, cutting a 

 little to one side of the middle line, thus reducing 

 the whole to a condition of vertical lo?igitudinal 

 section. Examine from within. 



a. The cranial and 7iasal cavities ; note their limits 

 and mutual relationships. 



(i. The septum nasi ; a median plate of cartilage, 

 separating the two nasal chambers in the middle- 

 line (examine from the front). 



y. The sphenethmoid. Seen to consist of a pos- 

 terior cranial portion which embraces the an- 

 terior third of the brain-case, and an anterior 

 paired portion, which is similarly related to the 

 bases of the olfactory capsules. 



8. The exoccipital and pro-otic. Examine these in 

 relation, as seen from within (cf. § 4 (^.). 



€. The fronto-parietal^ nasal ^ vomer, and para- 

 sphenoid (if in place). Examine, in relation to 

 the chondro-cranium. 



t,. The rhi?ial process (cf § b. y.) ; seen to form a 

 support for the pre-maxilla, abutting against its 

 inner face. 



rj. The /oramina for exit of the cranial nerves — as 

 under, on one side. 



i. The olfactory foramen (L Cranial) ; a perfora- 

 tion of the partition between the two portions 

 of the sphenethmoid. 



ii. The optic foramen (II. Cranial); obvious as a 

 perforation of an oval membraneous area of 

 the side wall a short distance behind the 

 sphenethmoid. 



