138 



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 vomeronasal organ, 



Fig. 62. TIi p skull in vertical section : BO, basioccipital (basilar portion of occipital) ; 

 BS basisphenoid (bodv 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; 



Y, vomer. .... , . .. , 



a. p.. piriform aperture of nose; c.f., internal aperture of facial canal; c.o., occipital 

 condyle; f.c.a., f.c.m. and f.c.p., anterior, middle, and posterior cranial fossae; f.f., floccular 

 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; o., 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 



