THE SKULL AS A WHOLE 127 



transmits the third, the fourth, the three branches of the ophthalmic division 

 pf the trigeminal, the abducent nerve, some filaments from the cavernous plexus 

 if the sympathetics, the orbital branch of the middle meningeal artery, a recurrent 

 branch from the lacrimal artery to the dura, and the ophthalmic vein. Behind 

 the inner extremity of the sphenoidal fissure is the foramen rotundum, for the passage 

 }f the second division of the trigeminal nerve; still more posteriorly is seen a small 

 >rifice, the foramen Vesalii, an opening situated between the foramen rotundum 

 and the foramen ovale, a little internal to both; it varies in size in different indi- 

 Hduals, and is often absent; when present it transmits a small vein and opens below 

 into the outer side of the scaphoid fossa. Behind and external to the latter open- 

 ing is the foramen ovale, which transmits the third division of the trigeminal nerve, 

 jthe small meningeal artery, and sometimes the small petrosal nerve. On the 

 juter side of the foramen ovale is the foramen spinosum, for the passage of the middle 

 meningeal artery; occasionally a small foramen (canaliculus innominatus) for the 

 transmission of the small superficial petrosal nerve is seen internal to the fora- 

 men spinosum. On the inner side of the foramen ovale is the foramen lacerum 

 medium; the lower part of this aperture is filled in the recent state with cartilage 

 khich is pierced by. the Vidian nerve and a meningeal branch from the ascending 

 )haryngeal artery. On the anterior surface of the petrous portion of the temporal 

 )one is seen, from without inward, the eminence caused by the projection of the 

 superior semicircular canal ; in front of and a little outside this is a depression cor- 

 "esponding to the roof of the tympanum; the groove leading to the hiatus Fallopii, 

 'or the transmission of the petrosal branch of the Vidian nerve and the petrosal 

 Branch of the middle meningeal artery; beneath it, a smaller groove, for the, pas- 

 sage of the lesser petrosal nerve; and, near the apex of the bone, the depression 

 'or the Gasserian ganglion; and the internal orifice of the carotid canal, for the 

 massage of the internal carotid artery and carotid plexus of nerves. 



The posterior fossa (fossa cranii posterior}, deeply concave, is the largest of the 

 three, and situated on a lower level than either of the preceding. It is formed by 

 he posterior third of the superior surface of the body of the sphenoid, by the occipi- 

 al, the petrous and mastoid portions of the temporal, and the posterior inferior 

 angle of the parietal bones; it is crossed on either side by four sutures, the petro- 

 occipital, the masto-occipital, the mastoparietal, and the basilar; and lodges the 

 cerebellum, pons, and medulla oblongata. It is separated from the middle fossa 

 n the median line by the dorsum sellaj, and on each side by the superior border 

 of the petrous portion of the temporal bone. This border serves for the attach- 

 ment of the tentorium cerebelli, is grooved for the superior petrosal sinus, and at 

 ts inner extremity presents a notch, in which rests the trigeminal nerve. The cir- 

 cumference of the fossa is bounded posteriorly by the grooves for the lateral (trans- 

 verse) sinuses. In the centre of this fossa is the foramen magnum, bounded on either 

 side by a rough tubercle, w r hich gives attachment to the odontoid or check liga- 

 nents; and a little above these are seen the internal openings of the anterior 

 condylar foramina, through which pass the hypoglossal nerves and meningeal 

 tranches from the ascending pharyngeal arteries. In front of the foramen mag- 

 num is a grooved surface, formed by the basilar process of the occipital bone and 

 the posterior third of the superior surface of the body of the sphenoid, which 

 supports the medulla oblongata and pons; and articulates on each side with the 

 aetrous portion of the temporal bone, forming the petro-occipital suture, the anterior 

 lalf of which is grooved for the inferior petrosal sinus, the posterior half being 

 encroached upon by the foramen lacerum posterius (foramen jugulare). This fora- 

 men presents three compartments through the anterior passes the inferior petrosal 

 sinus; through the posterior, the lateral sinus and some meningeal branches from 

 the occipital and ascending pharyngeal arteries; and through the middle, the 

 wlossopharyngeal, vagus, and spinal accessory nerves. Above the jugular foramen 



