DISSECTING MANUAL. 



orifice of a canal (internal auditory meatus), which runs out- 

 ward and slightly downward and ends blindly; its fundus 

 presents a horizontal ridge (falciform crest), the orifice of the 

 aqueductus Fallopii, and foramina for the auditory nerve 

 (see page 102). External to and above the meatus is a depres- 

 sion (floccular fossa) for a process of dura mater; below and 

 external to this is a foramen (of the aqueductus vestibuli) 

 which may be concealed by a scale of bone. A groove (for the 

 superior petrosal sinus) occupies the superior border of the 

 petrous temporal, while another (for the inferior petrosal sinus) 

 runs along the suture between the basi-occipital and petrous 

 temporal to the jugular foramen. [171] 



The squamous part of the occipital presents a mesial eleva- 

 tion (internal occipital protuberance) ; a ridge (internal occip- 

 ital crest) descends from this to the foramen magnum and is 

 grooved (for the occipital sinus) ; another ridge ascends from 

 the protuberance and presents a groove (sagittal sulcus) at 

 one side (for the superior longitudinal sinus) . From each side 

 of the protuberance a groove (for the lateral sinus) runs for- 

 ward and outward to the posterior inferior angle of the parietal, 

 and then downward and inward on the mastoid, the posterior 

 surface of the petrous temporal, and then the occipital, to the 

 jugular foramen: it presents the inner orifice of the mastoid 

 foramen ; its upper lip limits the posterior fossa laterally and 

 posteriorly. These sinuses meet (torcular Herophili) at one 

 side of the occipital protuberance. [171] 



THE CRANIUM IN SAGITTAL SECTION. 



Nasal Fossae. These are deepest at their centre. The floor 

 of each is formed by the palate process of the superior maxilla 

 and the horizontal process of the palate bone. The roof con- 

 sists of the nasal, frontal, cribriform plate of the ethmoid, body 

 of the sphenoid, sphenoidal turbinal, sphenoidal process of 

 the palate, and ala of the vomer. The outer wall consists of the 

 nasal, nasal process of the superior maxilla, lachrymal, lateral 



[16] 



