VISUAL REFLEXES 



407 



of visual impressions and visual movements with, the movements of every 

 part of the body, and especially with the complex mechanism we have already 

 studied in connection with the labyrinth and cerebellum. Stimulation of the 

 corpora quadrigemina therefore evokes movements of the eyes and of the 

 head ; extirpation of this part, even when bilateral, though it may inter- 

 fere with co-ordination, does not necessarily involve loss of sight. 



The multifarious intercourse which is continually taking place between 



o.c.m.n 



p./. 6: 



VJ/I.Vest.n 



Vest. spin. tract. 



liJS5r\Afl/*/>9S/s bundle 



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



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

 IV.n, nucleus of fourth nerve ; Vl.n, nucleus of sixth nerve ; D.N, Deiters' nucleus ; 

 S.O, superior olive ; VIII. Vest.n, vestibular nerve ; p.l.b, posterior longitudinal 

 bundle ; 1st c.n, first cervical nerve. 



the eye centres and those for the movements of the body, and between 

 afferent impressions from the eyes and those from the semicircular canals and 

 the proprioceptive system generally, is effected to a large extent through the 

 intermediation of the posterior longitudinal bundle, which extends through- 

 out the whole length of the mid-brain and the hind-brain, and in the spinal 



