13g, ANATOMY OF THE RABBIT. 
the nasal septum (septum nasi), or cartilaginous portion of the 
mesethmoid. This is continuous posteriorly with a _ small 
crescentic vertical plate of bone, the perpendicular plate (lamina 
perpendicularis) of the ethmoid bone—the bony portion of the 
mesethmoid—and the latter is also the terminal element of the 
series of median bones constituting the basicranium. Posteriorly, 
the ventral portion of the cartilaginous nasal septum is supported 
by a vertical bony plate, the vomer, the dorsal margin of which 
is grooved to receive it. Anteriorly, the nasal septum bears on 
its ventral margin the paired enclosures of the yomeronasal organ, 

Fic. 62. The skullin vertical section: BO, basioccipital (basilar portion of occipital) ; 
BS, basisphenoid (body of posterior sphenoid); ET, ethmoturbinal; F, frontal; I, inter- 
parietal; M, maxilla; MT, maxilloturbinal; N, nasal; NT, nasoturbinal;. P, parietal; 
PL, palatine; PMX, premaxilla; PR, presphenoid (body of anterior sphenoid) ; PT, petrous 
portion of petromastoid; SO, supraoccipital (squamous portion of occipital); T, tympanic; 
V, vomer. 
a.p., piriform aperture of nose; c.f., internal aperture of facial canal; c.o., occipital con- 
dyle; fc.a., f.c.m. and f.c.p., anterior, middle, and posterior cranial fossae; f.f., parafloccular 
fossa; f.h., hypophyseal fossa; f.in., incisive foramen; f.s., sphenopalatine foramen; 1., per- 
pendicular plate of the ethmoid; m.a.i., internal acoustic meatus; 0., optic foramen; p.a., 
alveolar process of maxilla; p.d., hard palate; p.o.e., external occipital protuberance; 
p.pt., pterygoid process of posterior sphenoid; s.n., nasal septum; t.c., tentorium cerebelli. 
which are also supported by the grooved surface formed in the - 
middle line by the adjacent dorsal surfaces of the palatine processes 
of the premaxilla. The relations of these structures, as well as of the 
cartilage supporting the nasopalatine duct, are best seen in very 
young animals (cf. Plate III). 
The delicate, folded, or scroll-like turbinated bones, charac- 
teristic of the nasal cavity, are borne on its posterior and lateral 
walls. Occupying the anterior portion of the lateral wall of the 
nasal fossa is a finely-ridged mass of bone, the concha inferior, or 
maxilloturbinal. It is easily distinguishable from a more dorsal 
