NEUROLOGY 269 



and passes through a narrow bony canal in the base of the brain, 

 below the pathetic and the abducens, and through the foramen 

 ophthalmicum. It then enters the eye cavity above the optic nerve, - 

 and on the wall of the cavity extends downward, and with regard 

 to the eyeball, dorsally lying close to the rectus internus muscle 

 and close to the surface of the eyeball. It passes along the olfac- 

 tory nerve, extends under the superior olbique muscle, and finally 

 reaches the inner angle, or canthus, of the eye. It here divides into 

 the recurrent externa and the ethmoidalis. The ethmoidalis branch 

 is a straight continuation of the ophthalmic. It extends along close 

 to its fellow of the opposite side, and, over the vomer, splits into two 

 branches. The smaller of these branches breaks through the bone 

 cells of the jaw, continues upon its ventral surface in a furrow ex- 

 tending forward, and terminates in the gum region. It supplies the 

 gum and point of the beak. The larger branch enters into the cell 

 substance extending to the tip of the beak, in its course sending 

 out a number of fine filaments, which spread out along the outer 

 surface. At this point these two branches may fuse. The larger 

 branch is endowed with the sense of touch. 



The recurrent externa divides shortly after leaving the main trunk 

 of the eye cavity passes over the lacrimal gland. It gives two 

 branches to this gland and one to the membrana nictitans, and 

 innervates the upper eyelid. It then emerges from the eye cavity, 

 passing over the os lacrimale, and gives one or more branches to 

 the integument of this region, including the comb. This branch 

 is large in birds with a large comb. Branches pass in front of the 

 lacrimal bone through the outer nasal cavity and into its deeper 

 structure. 



Shortly after the ophthalmic branch has entered into the eye 

 cavity and before it crosses the optic nerve, it gives a fine branch 

 to the motor occuli. 



The second and the third branches of the fifth cranial nerve are 

 mixed. They contain elements of both the portio major and the 

 portio minor. These two branches come from the lower part of the 

 outer region of the ganglion, and pass together through a cavity 

 which is located between the os petrosum and alae and basis sphe- 

 noid, and then branch. 



The ramus secundus, or superior maxillary division, of the tri- 

 facial, is the second branch and passes into the orbit below the 

 optic nerve and the eyeball. It is called the recurrent infra -orbitale. 



