v///-: 



side tn side ainl almost smooth. Tho 

 .!<>i; inti-ntiil, or nnxnl face exhibits a ver- 

 ticil crest passing along the external border 

 of the bone, which gives attachment to the 

 nated portion of the ethmoid; at its supe- 

 rior extremity this crest bifurcates, and between 

 its two branches shows a concave surface which 

 forms part of the frontal sinus. For the 

 remainder of its extent the internal face is 

 smooth, and covered by the mucous membrane 

 of the nasal fossa ; it is also excavated into a 

 channel to form the superior meatus of this 

 cavity. 



Borders. Tho > .rf< run! border is very thin 

 in its upper two-thirds, and articulates with 

 the lachrymal bone, the anterior border of 

 the supermaxillary, and the upper extremity 

 of the preinaxillary bones. In its lower third 

 it becomes isolated from the latter bone, in 

 forming with the anterior border of its large 

 process a very acute re-entering angle whose 

 opening looks downwards. The internal border 

 is denticulated to correspond with the opposite 

 bone. 



Base and Summit. Tho base occupies the 

 superior extremity of the bone ; it describes 

 a curved line with the convexity above, and in 

 uniting on the median lino with that of the 

 opposite bone, forms a notch similar to that 

 of the heart figured on playing cards ; it is 

 bevelled at the expense of the internal plate to 

 articulate with the frontal bone. The summit 

 of the two nasal bones, which is pointed, 

 constitutes the nasal prolongation: the name 

 given to a single triangular process which 

 comprises all that portion of the nasal bones 

 separated from the premaxillaries by the ro- 

 :ng angle before mentioned. 



Structure and development. Almost entirely 

 compact in structure, it is developed from a 

 single centre. 



The 



8. Turbinated Bones. 



turbinated bones, two on each side, 

 t\\o irregular bony columns, wider 

 above than l>elow, compressed laterally, hol- 

 low. d internally, and lying vertically side by 

 side on tin: external wall of the nasal 1 

 which they divide into three meatuses or pas- 



They are distinguished into anterior and 



./ iiirliiiiiiti-tl bones. 

 Tin- '////.,/,,/ or xiipi'rlor, also named the 



i: A NI> VI:I:TICAI. 

 SECTION OK Tin: Hoi:si;'s III:.M>. 

 1, Condyloid foramen; -. Parietal 

 protuberance; .'!, Internal audi- 

 tory hiatus ; 4, CYn-ln-al cavity ; 

 5, Cerebellar cavity ; li, SII|M>- 

 rior border of the MrpendJcnJtt 

 plate of the ethmoid bone (crista- 

 galli process); 7, Kthmoidal 



volute, -na>al lac- ; S, V, 



of the rijjht frontal MIIL 

 Ditto of tin- ^iiln'iinidal .-inns; 

 10, Ptt-ry^oid jirot'oss ; 11, Ktli- 

 nioidal turliinated Ix.ne; 1'J, 

 Maxillary turliinat.'.l bOMJ !, 

 Crest of tin- >u| i-i in.ixillary 

 bone tn which tin- latti-r is : 

 14, VoniiT. A, Orilici- nf com- 

 munication In-twrvn the nasal 

 i-avitv an<l tin- sinus. 



