BOXES OF THE HEAD. 



form the internal and external anejular processes. Tlie internal is but 

 sliti-litly marked ; the external is strong and projecting, and articulates 

 -with the malar bone. The temporal ridge springs from the external 



•«p^ 



Fig. 31. — Frontal Bonk FKo:\t 



BEFORE, SHOWING ITS EXTER- 

 NAL Surface. (A. T.) 4 



1 , fi'ontal eminence ; 2, nasal 

 spine, and above this the ser- 

 rated surface for articulation of 

 the nasal and suiierior maxil- 

 lary bones ; 3 to 4, .supra-orbital 

 edge — 3, internal, and 4, exter- 

 nal angular process ; 5, supra- 

 orbital notch or foramen; 6, 

 glabella ; 7, superciliary emin- 

 ence and ridge ; 8, temporal 

 ridge, and behind this a part of 

 the temporal fossa. 



process, and arches up- 

 wards and backwards to 

 be continued on the 

 parietal bone : it separ- 

 ates the temporal from 

 the frontal part of the 

 outer surface of the bone. 

 Inferior surface. — The orbital sarfa,ces are somewhat triangular, 

 their internal margins being parallel, while the external are directed 

 backwards and inwards. Close to the external angular process is the 

 fossa laclLrijmalls, which lodges the lachrymal gland ; and close to the 

 internal angular process is a small impression where the pulley of the 

 trochlearis muscle is attached. Between the orbits in front is tile 

 serrated surface which articulates with the superior maxillary and nasal 

 bones, and in the middle line a sharp process of variable length, the 

 nasal spine, descends between the latter bones and the central plate of 

 the ethmoid. Between the incisura ethmoidalis and the inner margin 

 of the orbit is an irregular surface occupied with de])ressions forming 

 the roofs of cells in the ethmoid bone. Traversing this surface are two 

 grooves, which complete, with the ethmoid, the anterior and posterior 

 internal orhital foramina. The anterior groove transmits the nasal twig 

 of the ophthalmic nerve and the anterior ethmoidal vessels ; the other, 

 the posterior ethmoidal vessels. Further forwai'd, on each side of the 

 nasal spine, is the larger opening of the frontal sinus, a cavity whicli 

 extends within the bone for a variable distance behind the superciliary 

 ridges. Outside and behind the orbital surface, there is a lai'ge serrated 

 triangular area which articulates with the great wing of the sphenoid. 



Cerebral surface. — This surface forms a large concavity, except over 

 the roofs of the orbits, which are slightly convex. Upon it are seen 

 the impressions of the cerebral convolutions, which, with the inter- 

 vening ridges, are strongly marked over the orbits. A groove, the 

 sukus frontalis, lodging the longitudinal sinus, descends from the 

 middle of the upper margin of the bone, and is succeeded by the crista 

 frontalis, a ridge which runs dovrn to the lower margin. A small fora- 

 men, usually formed in part by the central plate of the ethmoid, is 



