THE CENTRAL NERVOUS SYSTEM 



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the frontal fibres are known, and those of the occipital and 

 temporal fibres are supposed, to be situated in the cortex. 

 Running on through the crusta of the cerebral peduncle 

 (Fig. 249), the frontal tract internal, the occipito-temporal 

 external, they end in the grey matter of the pons, and 

 probably serve as one segment of an extensive commissural 

 connection between the cerebral and the cerebellar cortex of 

 the opposite side, the other segment being formed by neurons 

 whose cell-bodies are situated in the pons, and whose axons, 

 crossing the middle line, pursue their course through the 

 middle cerebellar peduncle, to terminate as the so-called mossy 



FIG. 251. ASSOCIATION FIBRES (AFTER STARR). 



Cerebral hemisphere seen from the side. A, A, association fibres between adjacent 

 convolutions ; B, between frontal and occipital lobes ; C, cingulum, connecting frontal 

 and temporo-sphenoidal lobes ; D, uncinate fasciculus between frontal and temporal 

 regions ; E, inferior longitudinal bundle between occipital and temporo-sphenoidal 

 lobes; O.T., optic thalamus ; C.N., caudate nucleus. 



fibres in the superficial grey matter of the cerebellum. It is 

 evident that the junction of the cerebral cortex with this 

 pontine grey matter, through and into which so many nerve- 

 tracts pass, multiplies the number of possible routes by which 

 impulses may travel between one part of the brain and 

 another. The corpus callosum forms a mighty link between 

 the two cerebral hemispheres. And intertwined in the corona 

 radiata with the callosal fibres are other systems, of which 

 it is especially necessary to mention the fibres that join 

 nearly every part of the cerebral cortex with the optic 



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