THE CRANIAL NERVES 281 



the median line. The deep origin of the large, sensory root is in 

 the pons immediately below the floor of the fourth ventricle and 

 just internal to its marginal boundary. The small, motor root 

 rises from a point just internal to the large root. 



Course and Distribution. The two roots, taking their origin 

 as above described, pass through the dura above the internal 

 auditory meatus and run along the superior border of the petrous 

 portion of the temporal bone to a point near its apex, where a 

 large ganglion, the semilunar or Gasserian, is developed on the 

 posterior root and occupies a depression on the bone for its re- 

 ception. The motor root passes beneath the ganglion without 

 being connected with it. 



The posterior root will be first followed to its distribution. 



From the anterior surface of the Gasserian ganglion are given 

 off three branches (i) ophthalmic, (2) superior maxillary, 

 (3) inferior maxillary. After the inferior maxillary has left 

 the cranial cavity it receives fibers from the small or motor root, 

 but the other branches are composed entirely of fibers from the 

 sensory root. 



i. The Ophthalmic Branch passes forward along the outer 

 wall of the cavernous sinus, divides into three branches (a) 

 lachrymal, (b) frontal, (c) nasal and enters the orbit by 

 the sphenoidal fissure. It communicates with the cavernous 

 sympathetic, third and sixth nerves, (a) The lachrymal 

 branch, running along the outer wall of the orbit, reaches the 

 lachrymal gland, gives off filaments to it and to the conjunctiva/ 

 and pierces the tarsal ligament to be finally distributed to the 

 integument of the upper lid. (b) The frontal branch runs 

 along the upper wall of the orbit and separates into the supra- 

 trochlear and supra-orbital branches. The former of these 

 leaves the orbit in front and turns up over the bone to supply the 

 integument of the lower forehead; the latter traverses the supra- 

 orbital canal, escapes by the foramen of the same name, and 

 supplies the skin as far back as the occiput as well as the peri- 



