836 



NEUROLOGY 



gray cortex, continuous with that of the uncus; in front it is continuous with the 

 putamen, behind with the stria terminalis and the tail of the caudate nucleus. 



The internal capsule (capsula interna) (Figs. 745, 746) is a flattened band of white 

 fibers, between the lentiform nucleus on the lateral side and the caudate nucleus 

 and thalamus on the medial side. In horizontal section (Figs. 742) it is seen to be 

 somewhat abruptly curved, with its convexity inward; the prominence of the curve 

 is called the genu, and projects between the caudate nucleus and the thalamus. 

 The portion in front of the genu is termed the frontal part, and separates the len- 

 tiform from the caudate nucleus ; the portion behind the genu is the occipital part, 

 and separates the lentiform nucleus from the thalamus. 



Corpus callosum 



Anterior corm. 

 Cavity of septum 

 pellucidum 



Columns of 

 fornix 



Anterior 

 commissure 



Third ventricle 



Optic 

 chiasma 



Globus pallidus 

 Claustrum 

 Insula 



Fia. 744. Coronal section of brain through anterior commissure. 



The frontal part of the internal capsule contains: (1) fibers running from the 

 thalamus to the frontal lobe; (2) fibers connecting the lentiform and caudate 

 nuclei; (3) fibers connecting the cortex with the corpus striatum; and (4) fibers 

 passing from the frontal lobe through the medial fifth of the base of the cerebral 

 peduncle to the nuclei pontis. The fibers in the region of the genu are named 

 the geniculate fibers ; they originate in the motor part of the cerebral cortex, and, 

 after passing downward through the base of the cerebral peduncle with the cerebro- 

 spinal fibers, undergo decussation and end in the motor nuclei of the cranial 

 nerves of the opposite side. The anterior two-thirds of the occipital part of the 

 internal capsule contains the cerebrospinal fibers, which arise in the motor area 

 of the cerebral cortex and, passing downward through the middle three-fifths of 

 the base of the cerebral peduncle, are continued into the pyramids of the medulla 

 oblongata. The posterior third of the occipital part contains: (1) sensory fibers, 

 largely derived from the thalamus, though some may be continued upward from 



