CENTRAL NERVOUS SYSTEM. 



677 



interruption in the thalamus. 1 Fig. 179, as will be observed, shows no fibres 

 running directly to the cortex without interruption in the thalamus. It will 



Cortex. 



Internuclear 



( Eeticular 

 < formation 

 ( pons, bulb 



( Ventral 

 < thalamic 

 I nucleus. 



( Nucleus 

 < of dorsal 

 I columns. 



FIG. 179. To illustrate the pathway of a sensory impulse arriving at the nuclei of the dorsal columns 

 "d" or the gray matter of the pons and bulb " c." The impulse is represented as passing over to a new 

 element "a" in the thalamic nuclei, and from thence to the cortex. In the other direction the cortex 

 is shown as connected with the thalamic cells by tne neuron &'; only the fibres arising from the nuclei 

 of the dorsal columns cross the middle line "meson" (von Monakow). 



be noted that these fibres of the dorsal columns are physiologically joined with 

 the contralateral thalamus and hemisphere. In part, however, the neurons from 

 the dorsal nuclei enter the cerebellum by the inferior peduncle of the same side. 

 The ascending fibres in the lateral columns of the cord pass to the cerebellar 

 hemisphere of the same side by way of the inferior peduncle of the cerebel- 

 lum, and, although the paths out of the cerebellum are not clearly marked, 

 the general relation of the hemispheres of the cerebellum to that of the cere- 

 brum is a crossed one. Some of the fibres by which this crossed connection 

 is accomplished pass from the cerebral hemisphere along the cms of the same 

 side to the olivary body, and thence by way of the arcuate fibres of the pons 

 and the middle peduncle to the opposite cerebellar hemisphere. 



It is with the " motor " region of the cerebral hemisphere that this con- 

 nection of the cerebellum appears to be most marked. If this really repre- 

 1 von Monakow : Archiv fur Psychiatric und Nervenkrankheiten, 1895, Bd. xxvii. 



