OSTEOLOGY. 9 



In the median line is the frontal crest, which gives attach- 

 ment to the falx cerebri and terminates below in a foramen, 

 the foramen caecum, for passage of a small vein from the nose 

 to the longitudinal sinus. The crest is grooved for longitudinal 

 sinus, and has on either side of it depressions for the Pacchionian 

 bodies. This surface is also grooved for anterior meningeal ar- 

 teries. 



The horizontal portion consists of an external and internal 

 surface. 



The external surface is concave, to form the roof of the 

 orbit, and separated from the opposite side by the ethmoidal 

 notch. 



FIG. 3. 



I, Superior border; 2, inferior border for squamous portion of tem- 

 poral; 3, anterior border for frontal bone; 4, posterior border for 

 occipital; 5, parietal eminence; 6, parietal foramen; 7, anterior in- 

 ferior angle. 



To the outer side is a deep depression for the lachrymal 

 gland, and to the inner side a slight one for the pulley of 

 superior oblique. 



On the margin of the orbital plate are two notches con- 

 verted into foramina by articulation with the ethmoid, the an- 

 Irrior ethmoidal canal, for passage of nasal nerve and anterior 

 dhinoidal vessels, and the posterior ethmoidal canal, for passage 

 of posterior ethmoidal vessels. 



The internal surface is marked by the convolutions of the 

 anterior lobes of the brain. 



Between the two plates of the vertical portion are the frontal 

 sinuses, two irregular cavities lined with mucous membrane and 

 opening into the middle meatus of the nose on either side by the 

 infundibulum. 



It articulates with twelve bones, two parietal, sphenoid, 

 ethmoid, nasal, superior maxillary, lachrymal, and malar. 



