NERVES OF ENCEPHALON. 423 



in the middle fossa, on the anterior cerebral surface of the 

 petrous bone, into the Casserian ganglion. This ganglion 

 is of a semilunar shape, and presents, on removing the dura 

 mater, a dark and flat appearance, with its filaments mat- 

 ted or having the plexiform arrangement. On raising this 

 ganglion, the smaller motor or anterior root will be seen to 

 pass on its under surface without any adhesion. It is easily 

 separated and may be traced on to the inferior maxillary 

 nerve, with which it unites. 



Three large branches proceed from this ganglion, the oph- 

 thalmic, the superior, and the inferior maxillary nerves. The 

 first enters the orbit through the foramen lacerum superius, 

 and supplies the eye and its appendages with common feel- 

 ing or general sensibility ; the second or superior maxillary 

 is distributed to the upper jaw and face, supplying these 

 parts also with sentient nerves ; the third or inferior maxil- 

 lary nerve is the largest branch and passes through the fora- 

 men ovale. Its motor portion supplies the muscles of mas- 

 tication, as the temporal, masseter, pterygoid, and buccina- 

 tor, while the sensitive goes to the lower jaw, tongue, chin, 

 lips, &c. 



Sixth Prir, Motor es Externi or Abducentes Oculi, (Fig. 118.) 

 This pair is of a size between the third and fourth. Each 

 nerve arises from the superior extremity of the corpus pyra- 

 midale, close to the pons, passes forward to the body of the 

 sphenoid bone, where it penetrates the dura mater, courses 

 the cavernous sinus on the outside of the carotid, enters the 

 orbit through the foramen lacerum superius, and goes to 

 the rectus externus muscle. The root of the nerve has been 

 traced through the corpora pyramidalia into the gray 

 matter of the olivary bodies. 



Seventh Pair, Portio Dura and Portio Mollis, (Figs. 16, 

 109.) This pair is regarded by some as two distinct nerves, 

 and so divided. The portio dura is the smaller of the two, and 

 arises from the upper part of the medulla oblongata close to 

 the lower part and side of the pons, below the crus cerebelli 

 and in front of the corpus restiforme, into the gray neurine 

 of which its fibres can be traced. It is called the facial 



