NERVOUS SYSTEM. 



55 



the cerebellum, which 

 enter the posterior 

 portion of the optic 

 lobes. The habenulae 

 are also to be re- 

 garded as longitudi- 

 nal tracts ; while the 

 for nix, a part of 

 which lies ventral to 

 the corpus callosum 

 (infra), is to be 

 placed in the same 

 category, although 

 its fibres seem in 

 places to run transversely. 

 Among the transverse 

 fibres most constant are the 

 anterior and posterior com- 

 missures in the region of 

 the twixt brain. 1 The an- 

 terior crosses from side to 

 side in the anterior wall of 

 this region, the other is 

 nearer the junction of twixt 

 brain and optic lobes. In 

 the higher vertebrates the 

 cerebral hemi- 



FIG. 57. Diagram of fibre 



spheres are con- tracts in mammalian brain> 



nected by a large after Jelgersma. C, cortex 



of cerebrum ; CB, cortex of cer- 

 ebellum ; CF, centrifugal tract ; FO, centrifugal tract to 

 olivary nucleus; GR, nucleus ruber ; ND, dentate nucleus 

 of cerebellum; NO, nucleus olivarius inferior; OC, crossed 

 connective between olivary nucleus and the vermis; P, gan- 

 glion of the pons; PC, dorsal tract from the pontal ganglion to 

 the cerebellar cortex of the opposite side ; PD, pyramid tract ; 

 PDC, tract from the pedunculus cerebelli to the cerebrum ; 

 R T, fibre course from nucleus ruber to optic thalamus ; TC, connection of 

 with cerebral cortex ; THO, optic thalamus ; VPC, ventral tract from portal 

 to cerebellar cortex of the opposite side. 



1 The so-called median commissure is not a fibre tract. 



thalamus 

 ganglion 



