THE FRONTAL BONE. 



37 



the orbits, from before backwards, with the nasal, superior maxillary, lachrymal, and 

 ethmoid bones. 



Anterior surface. The part forming the greatest convexity of the forehead on 

 each side is called the frontal eminence. It is separated by a slight depression below 

 from the superciliary ridge, a curved elevation of varying prominence above the 



NASAL SPINE 



NASAL SURFACE 



ASAL NOTCH 



TROCHLEAR FOSSA 



.FRONTAL SINUS 



LACHRYMAL FOSSA 



EXT. AMG PROC- 



NT. ORB. CANALS 

 ETHMOIDAL NOTCH 



FIG. 37. FRONTAL BONE, FROM BELOW. (Drawn by D. Gunn.) 



.NT. ETHM. CELL 



margin of the orbit. Between the superciliary ridges is the surface called glabella. 

 The margin of the orbit, the orbital arch, is most defined towards its outer, part ; it 

 presents towards its inner third the supraorbital notch, sometimes a foramen, which 

 transmits the supraorbital nerve and artery. The extremities of the orbital 

 arch point downwards, and form the internal and 

 external annular processes : the internal is but slightly 



** L * M1SAI RONE 



marked ; it meets the lachrymal bone : the external is 

 strong and projecting, and articulates with the malar 

 bone. The temporal crest springs from the external 

 angular process, and arches upwards and backwards to 

 be continued into the temporal lines of the parietal 

 bone : it separates the temporal from the frontal part 

 of the outer surface of the bone. 



Inferior surface. The orbital surfaces are some- 

 what triangular, their internal margins being parallel, 

 while the external are directed backwards and inwards. 

 Close to the external angular process is the lachrymal 



fossa, which lodges the lachrymal gland ; and close to the internal angular pro- 

 cess is a small depression, trochlear fossa, where the pulley of the superior 

 oblique muscle is attached. Between the orbits in front is the nasal notch, 

 bounded by a narrow semilunar serrated surface which articulates with the upper 

 ends of the nasal bones and the nasal processes of the superior maxillae. Occu- 

 pying the concavity of the notch is the nasal process (Henle), which projects 

 beneath the nasal and maxillary bones, supporting the bridge of the nose. On 

 the posterior aspect of the nasal process are a small grooved surface on each 

 side, which enters into the formation of the roof of the nasal fossa, and a 



Fig. 38. TRANSVERSE SECTION OF 



THE BRIDGE OF THE NOSE. 



(G. D. T.) 



