GE SENSE? CAPSULES. 21 
an upper and posterior portion, which 
‘forms the inferio-anterior portion of 
the brain-case, the eribriform plate. 
It is perforated with numerous small 
holes, through which the divisions of 
the olfactory nerve pass to: the nose. 
The lower and anterior portion, the 
lamina perpendicularis forms a ver- 
tical plate immediateiy in front of the 
cribriform plate: its anterior border 
is produced and forms a vertical 
cartilaginous plate, the septum nasi; 
the two forming a partition between 
the right and left olfactory cavities. 
THE SENSE-CAPSULES. 
At an early stage in the development of the dog, 
the olfactory, optic, and auditory organs become 
enclosed from their ventral surface by cartilage; 
the lateral walls of the basal plate extend up- 
wards and inwards, ultimately enclosing the 
whole of the sense organs, and, in some verte- 
brates, part or all of the dorsal surface. Such 
a cartilaginous skull, however, does not persist 
in any of the mammalia, but in some fishes, 
e.g. Elasmobranches, it forms.the skull (chon- 
docranium) of the adult. In the higher Verte- 
brata, cartilaginous capsules ossify from certain 
centres and form bones. The position, form, 
