42 THE SKELETON OF THE CAT. 



Nasal Bone. Os nasale (Fig. 30). — The nasal bones fill 



the space between the nasal process of the premaxillary, the 



frontal process of the maxillary, and the nasal spine 



of the frontal bone (Fig. 39, 7). They thus form 



part of the dorsal wall of the nasal cavity near the 



middle line. 



Each may be described as consisting of two 



elongated triangular lamella;, one vertical, the other 



horizontal. The vertical lamella is curved slightly 



30- ventrad and has its apex directed craniad. It is 



Nasal Bone, ,. , , . ,• , r • i • i 



Do u SAL applied by its medial suriace against the vertical 



View. lamella of the opposite bone, the two thus forming 



a median vertical partition, the nasal crest (Fig. 43, 12), which 



extends ventrad into the nasal cavity and, by joining the dorsal 



edge of the lamina perpendicularis, helps to form the internasal 



septum. 



The horizontal lamella is attached to the dorsal margin of 

 the vertical lamella in such a way that its apex lies opi)osite 

 the base of the vertical lamella. It helps to roof in the nasal 

 cavity, and by its base forms a part of the dorsal boundary of 

 the narial opening. By its lateral margin it articulates with 

 the nasal spine of the frontal at its caudal end, with the frontal 

 process of the maxillary at its middle, and with the nasal process 

 of the premaxilla at its cranial end. The lateral angle of its 

 base projects in a curved line which forms the dorsal part of 

 the lateral boundary of the narial opening. 



From the lateral border of the horizontal lamella a bony 

 plate curves ventrad and mediad, enclosing a narrow fossa which 

 receives a part of the ethmoid. This is the concha nasalis 

 superior (nasoturbinal bone). 



Ethmoid Bone. Os ethmoidale (Figs. 31 and 32). — The 

 ethmoid bone closes in the cranial cavity at its cranial end and 

 extends forward into the nasal cavity, which it largely fills. 



It consists of a median vertical portion, the lamina perpen- 

 dicularis (Fig. 43, ;/; Fig. 42, p), forming a part of the nasal 

 septum, of two lateral portions made of thin sheets of bone 

 variously folded and united — the labyrinths (or ethmotur- 

 binals), which fill the greater part of the nasal cavity; and of 



