268 ANATOMY OF THE DOMESTIC FOWL 



somatic column close below and somewhat aside from the aqueduct 

 of Sylvius. The nerve leaves the brain cavity through a distinct 

 foramen near the foramen opticum, and supplies the following eye 

 muscles: fixst, after entering the orbit, it sends a branch upward 

 to the inferior portion of the inferior rectus; then, it gives off the 

 thick ramus ciliaris. The trunk then extends under the optic 

 nerve and passes forward to innervate the inferior rectus, the 

 internal rectus, and the inferior oblique. A ciliary gangUon forms 

 on the trimk. 



The Patheticus. — (Fig. 62, No C, 11) is a small motor nerve, 

 originating close to the sulcus centralis, in the circle of the center 

 brain over the valve of Vieussens, between the posteriors of the 

 optic lobes. It extends in a dorsal direction between the cere- 

 bellum and the lobus opticus, to the posterior of the latter of 

 which it then forms a loop ventrally. Lying close to the optic 

 foramen it passes through a fine opening into the eye cavity and 

 supphes the superior obHque muscle of the eye. During its course 

 it passes dorsally over the optic nerve, and then crosses dorsally 

 over the ophthalmic division of the fifth pair of cranial nerves and 

 the internal rectus muscle. 



The Trifacialis.— (Fig. 62, No C, 12). This, the fifth cranial, 

 is a mixed nerve and is divided into two parts, portio major and 

 portio minor. 



The portio major originates in the gangUon cells of the posterior 

 part of the brain. Commencing near the medulla oblongata it 

 passes through the posterior part of the brain, then upward and 

 outward; and along its route it forms the Gasserian gangUon, which 

 hes partly in the cranial cavity or in its wall. 



The portio minor consists of the downward passing fibers contain- 

 ing the motoric elements which are distributed to the muscles of the 

 jaw and of the eye. The roots are found in the gangUon from the 

 center and back brain, close below the pathetic nerve origin, where 

 the pathetic passes between the lobus opticus and the pars pedun- 

 cularis; it then takes a lateral course between the two. 



The fibers of the portio minor do not take part in the formation 

 of the Gasserian gangUon, but are only partly surrounded by it. 



There are three nerve trunks given off of the trifaciaUs: the oph- 

 thalmic, the superior maxiUary, and the inferior maxUlary. 



The ophthalmic division of the fifth nerve is the smaUest of the 

 three branches. It emerges directly from the Gasserian gangUon, 



