DISSECTING MANUAL. 



a ridge (inferior curved line) runs transversely outward on 

 each side. [165] 



THE CRANIUM IN TRANSVERSE SECTION. 



Deep Surface of Vault. There is a mesial sagittal groove 

 for the superior longitudinal sinus, with depressions on each 

 side for Pacchionian bodies. The parietal foramina lie on 

 either side of the sagittal suture just in front of the lambda. 

 The meningeal arteries groove the frontal and parietal. [167] 



Upper Surface of Base. This is divided into three 

 fossae. 



Anterior Fossa. This lies in front of the posterior edges 

 of the lesser wings of the sphenoid. Its floor is formed mesially, 

 from before backward, by the ethmoid and body of the sphe- 

 noid; and laterally by the orbital plates of the frontal and 

 lesser wings of the sphenoid. Anteriorly a ridge (frontal crest) 

 on the frontal, which descends from a groove (frontal sulcus), 

 is separated by an orifice (foramen caecum) from a mesial longi- 

 tudinal eminence (crista galli) of the ethmoid. A groove (for 

 the olfactory lobe) lies on either side of the crista galli and 

 presents many foramina (cribriform plate) leading to the nose; 

 on its outer side are two (anterior and posterior ethmoidal) 

 foramina leading to the orbit. [167] 



Middle Fossa. This extends from the lesser wings of the 

 sphenoid to the superior borders of the petrous bones. Its 

 floor is formed by the body and great wings of the sphenoid, 

 the squamous temporal, and the superior surface of the petrous 

 temporal. From before backward in the midline the body of 

 the sphenoid presents, first a transverse (optic) groove which 

 leads into the orbit on each side through a foramen (optic) 

 between the roots of the lesser wing. Behind this is a trans- 

 verse elevation (olivary eminence) from the back of whose 

 outer ends little spurs (middle clinoid processes) may project. 

 Behind this it presents a depression (sella turcica, or pituitary 

 fossa) which is overhung behind by a sloping ridge (dorsum 



[14] 



