PATHS FROM AND TO THE CORTEX 



855 



the middle line, pursue their course through the middle cerebellar 

 peduncle, to terminate in the superficial grey matter of the cere- 

 bellum. 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 afferent (cortipetal) fibres that join the optic thalamus 

 with nearly every part of the cerebral cortex. Such fibres pass from 

 the cells of the grey matter of the thalamus to the frontal and parietal 



Fig. 350. 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 temporr>.sphenoidal lobes; 

 D, uncinate fasciculus between frontal and temporal regions; E, inferior longi- 

 tudinal bundle between occipital and temporo-sphenoidal lobes; O.T., optic 

 thalamus; C.N., caudate nucleus. 



regions through the anterior border of the internal capsule in front of 

 the frontal fibres previously described as running in the anterior 

 limb of the capsule to the pons; and from the thalamus to the occi- 

 pital region through the extreme posterior border of the internal 

 capsule, behind the occipital fibres that proceed to the pons. The 

 fibres that connect the thalamus with the occipital cortex are 

 spoken of as the optic radiation. Some of the fibres of the optic 

 radiation, however, proceed, not from the thalamus, but from the 

 anterior corpus quadrigeminum and the lateral geniculate body. 

 The thalamus is also connected with the cortex of the temporal lobe, 

 with the cerebellum, and through the fillet with the posterior part of 

 the tegmental system, the medulla oblongata and the spinal cord 

 (p. 846). Fibres also pass from the inner and deeper part of the 

 thalamus to the lenticular nucleus of the corpus striatum. The 



