7 '///; I'KO.IWTIOX /'//; A'A'N o/-' ////; HEMISPHERES 



863 



nuis with tln> cortex belong to the projection system. Some of the Hiiro bundles of 

 the above systems h;ivo already been described in connection with the parts with 

 \\ liich t hey are ronrenicd. 



The projection fibres of the hemisphere comprise both ascending and descending 

 fibres between the cerebral cortex and structures below the bounds of the hemisphere, 

 i.e.. some arise in the structures below and terminate in the cortex: others arise 

 from the cortical cells and terminate in the structures below, including the grey 

 substance of the I halamencephalon. mesoneophalon, rhombencophalon, and spinal 

 cord. The projection fibres are given different names in the hemisphere according to 

 their arrangement and the appearances to which they contribute in the dissection-. 

 Beginning with the basis of the peduncle, they contribute (1) to the internal 

 cii/ixnlf and some to the uiirniil capsule- and (2) to the corona rmlintii. 



The internal capsule is a band of white substance, consisting of the ascending 

 fibres from the nuclei of the thalamus. hypothalamus. and corpus striatum, reinforced 

 by the descending fibres from the cortex to these nuclei and by those descending 

 in the cerebral peduncle to reach the structures below the prosencephalon. It is a 



FIG. 643. CORONAL SECTION THROUGH THE Sri.r.xirM OF THK CORPUS CALLOSUM AND THE 

 I'osTKiiiou COKNTA OF THK LATERAL VENTRICLES. (Viewed from behind.) (After Toldt, 

 "Atlas of Human Anatomy," Kubman, London and New York.) 



AM/)/. I IK IX ill-' i !,/./! S r\ I.I.I IXI'M 



S/'LK.\II-.V OF CORPUS CALLOSUM 



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broad, fan-like mass of fibres, which increases in width from the base of the hemi- 

 sphere upwards, and which is spread between the lenticular nucleus on its outer side 

 and the caudate nucleus and thalamus on its inner side. To reach the cortex above, 

 its fibres necessarily pass through the radiations of the corpus callosiim, and thus, 

 together with the corpus callosum, the fan-like bands of the two hemispheres form a 

 capsule containing t he t lialami. the third ventricle, the caudate nuclei, and the ante- 

 rior and central portions of the lateral ventricles. In sections, each internal capsule 

 appears bent at an angle, the genu, which approaches the cavity of the lateral 

 ventricle along the line of the boundary between the thalamus and the caudate nut-:. 



Along the genii rims the stria terminalis of the thalamus. and through the genu the 

 capsule receives fibres from the internal medullary lamina of the thalamus. from 

 the stratum xonale of the thalamus and from that of the caudate nucleus. At the 

 genu each capsule is separable into two parts: -(1) the frontal portion, spreading 

 between the caudate and lenticular nuclei: (2) the occipital portion, between the 

 lenticular nucleus and the thalamus. 



The corona radiata. Above the corpus callosum, and in part joining its radia- 



