644 



STRUCTURE OF THE CEREBRUM. 



[CH. XLVI. 



grey matter is called the cerebral cortex. The amount of this 

 grey matter varies directly with the amount of convolution of the 

 surface. Under it white matter is situated ; and at the base 

 there are masses of grey matter ; part of these basal ganglia are 

 seen forming part of the wall of the ventricles. The anterior 

 basal ganglion is called the corpus striatum; it is divided into 

 two parts called the lenticular or extraventricular 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. 



Fig. 478. 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., lenti- 

 cular nucleus ; c.i., internal capsule ; cl., claustrum ; c.e., external capsule ; m, corpus 

 maniniillare ; t.o., optic tract ; s.t.t., stria terminalis ; n.a., nucleus amygdalae ; cm, soft 

 commissure ; co.i., island of Eeil. (Schwalbe.) 



Passing up between the basal ganglia are the white fibres 

 which enter the cerebral hemisphere from the crus ; these consti- 

 tute 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. 478). 



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

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

 passes down into the fissures ; one very extensive set of convolu- 

 tions (co.i.} passes deeply into the substance of the hemisphere ; 

 this is called the Island of Reil ; the lowest stratum of grey 



