NERVES IN BASE OF SKULL. 



31 



Near the orbit the nerve is joined by one or two delicate filaments of 

 the cavernous plexus (p. 33). 



The FOURTH NERVE (fig. 4, 4 ) courses forwards, like the preceding, to 

 one muscle in the orbit. It is the smallest of the nerves in the wall of the 

 sinus, and is placed below the third ; but as it is about to pass through the 

 sphenoidal fissure it rises higher than all the other nerves. 



Fig. 4. 



The dura mater has been removed 

 in the middle fossa, on the left side, 

 to show the nerves in the wall of the 

 cavernous sinus, and especially the 

 ganglion, and the three trunks of the 

 fifth nerve. Each nerve, except the 

 first which is absent, is marked by its 

 corresponding numeral. On the right 

 side the dura mater is untouched, 

 f Offsets to the dura mater from the 

 fifth nerve. 



CRANIAL NERVES IN THE BASE OF THE SKULL. 



In the wall of the sinus the fourth nerve is joined by fwigs of the sym- 

 pathetic ; and it is sometimes united with the ophthalmic trunk of the 

 fifth. 



FIFTH NERVE (fig. 4, 5 ). This nerve is distributed to the face and 

 head, and consists of two parts or roots a large or sensory, and a small or 

 motory. 



The large root of the nerve passes through an aperture in the dura 

 mater into the middle fossa of the base of the skull, where it ends imme- 

 diately in the Gasserian ganglion. 



The ganglion of the root of the fifth nerve (Gasserian ganglion), placed 

 in a depression on the point of the petrous part of the temporal bone, is 

 flattened, and is nearly as \vide as the thumb-nail. The upper surface of 

 the ganglion is closely united to the dura mater, and presents a semilunar 

 elevation, whose convexity looks forwards. Some filaments from the 

 plexus of the sympathetic on the carotid artery join its inner side. 



Branches. From the front of the ganglion proceed the three following 

 trunks: The ophthalmic nerve, the first and highest, is destined for the 

 orbit and forehead. Next in order is the superior maxillary nerve, which 

 leaves the skull by the foramen rotundum, and ends in the face below the 



