654 



STRUCTURE OF THE CEREBRUM 



[CII. XLVI. 



divided into two parts called the lenticular or extraxentricular nucleus, 

 and the caudate or intraventricular nucleus. It has received the 

 latter name because it is seen in the interior of the ventricle. The 

 posterior basal ganglion is called the optic thalamus. 



Passing up between the basal ganglia are the white fibres which 

 enter the cerebral hemisphere from the crus; these constitute the 

 internal capsule. This passes in front between the two subdivisions 

 of the corpus striatum, and behind between the optic thalamus and 

 the lenticular nucleus of the corpus striatum. 



The relationship of these parts is best seen in a vertical section ; 

 such as is represented in the next diagram (fig. 476). 



CO. 



FIG. 476. Vertical section through the cerebrum and basal ganglia to show the relations of the latter, 

 co., cerebral convolutions; c.c., corpus callosum ; v.l., lateral ventricle; /, fornix; vIII., third 

 ventricle; n.c., caudate nucleus; th, optic thalamus ; n.l. .lenticular nucleus ; c.i., internal capsule ; 

 cl. t claustrum ; c.e., external capsule ; m, corpus mammillare ; t.o. } optic tract ; s.t.t., stria termin- 

 als ; n.a., nucleus amygdalae ; cm, soft commissure ; co.i., Island of Keil. (Schwalbe.) 



One hemisphere is seen, with portions of the other. The surface 

 darkly shaded indicates the grey matter of the cortex, which passes 

 down into the fissures ; one very extensive set of convolutions (co.i.), 

 passes deeply into the substance of the hemisphere; this is called 

 the Island of Eeil ; the lowest stratum of grey matter is separated 

 from this to form a narrow isolated strip of grey matter called the 

 claustrum (cl). In the middle line from above down are seen the 

 great longitudinal fissure extending as far as (c.c.) the corpus callosum, 

 the band of white matter that forms the great commissure between 

 the two hemispheres ; beneath this are the lateral ventricles which 

 communicate by the foramen of Munro with the third ventricle : the 

 fornix is indicated by the letter /. Contributing to the floor of the 

 lateral ventricle, one next sees the optic thalamus (th.), and the tail 



