VISUAL REFLEXES 



461 



On stimulating the floor of the iter, from before backwards we obtain 

 contractions in order of the rectus internus, the rectus superior, the 

 levator palpebrse superioris, the rectus inferior, and the inferior 

 oblique muscle. On stimulating more laterally, or exciting the 

 corpora quadrigemina, dilatation of the pupil was obtained. 



.-...AntC. Quad. 



Optic Tract 



Vlll.Vest.n 



Vest. spin, tract. 



rm basis bundle 



FIG. 205. Diagram of connections of posterior longitudinal bundle. 



Ant. C. Quad, anterior corpus quadrigeminum ; oc.ru.n, oculo - motor 

 nucleus ; IV.n, nucleus of fourth nerve ; Vl.n, nucleus of sixth nerve ; 

 D.N, Deiters' nucleus ; S.O, superior olive ; Vlll.Vest.n, vestibular nerve ; 

 p.l.b, posterior longitudinal bundle ; 1st c.n, first cervical nerve. 



It seems probable that the optic thalamus and the closely related 

 external geniculate body are mainly concerned with the reception 

 of visual impulses and their forwarding to the cerebral cortex. On 

 the other hand, the anterior or superior corpora quadrigemina are 

 mainly concerned with the co-ordination of visual impressions and 

 visual movements with the movements of every part of the body, 



