688 



STRUCTURE OF THE CEREBRUM 



[CH. XLVI11. 



divided into two parts, called the lenticular or extra-ventricular nucleus, 

 and the caudate or intra-ventricular 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 or leave the cerebral hemisphere by the crus ; these constitute 

 the internal capsule. This passes in front between the two subdivi- 

 sions 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. 425). 



FIG. 425. 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 tlialamus; n.l. .lenticular nucleus ; c.i., internal capsule; 

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

 alis ; n.a., nucleus amygdalae ; cm, soft commissure ; co.i., Island of Reil. (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 the great longitudinal fissure 

 is seen 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 com- 

 municate 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 thakrnus (th.), and the tail 



