878 



THE NERVOUS SYSTEM 



a medial portion of the roof of the inferior horn. It is separated from the thala- 

 mus adjacent to it by the stria terminalis of the thalamus (taenia semicircularis). 

 The end of its tail extends anteriorly below to the level of the anterior horn of the 

 ventricle above. Owing to its much curved shape, both horizontal and vertical 

 sections of the hemisphere passing through the inferior horn may contain the 

 nucleus cut at two places (see figs. 694 and 698.) 



The caudate nucleus is the intraventricular of the two masses of grey substance 

 which together are sometimes referred to as the basal ganglia. The extraventri- 

 cular of these masses is the lenticular Jiudeus, which is buried in the substance of 

 the hemisphere, laterally and inferior to the caudate nucleus. The two masses 



Fig. 691. — Diagrams of Lateral View and Sections op the Nuclei of the Corpus Stria- 

 tum WITH the Internal Capsule Omitted. 

 A and B below represent horizontal sections along the lines A and B in the figure above. The 

 figure also shows the relative position of the thalamus and the amygdaloid nucleus. 



Caudate nucleus 



^^,^r ^Thalamus 



Lenticular nucleus 

 Amygdaloid nucleus 

 Caudate nucleus 

 Thalamus 



Tail of caudate nucleus 



Internal capsule 

 Lenticular nucleus 



Caudate nucleus 

 Thalamus 



Tail of caudate nucleus 

 Internal capsule 



are separated by the internal capsule, a thick band of nerve-fibres continuous into 

 the cerebral peduncles, and connecting the grey cortex of the hemisphere with the 

 structures inferior to it. Anteriorly and below, the two nuclei become continuous 

 and the white substance of the internal capsule, in separating them posteriorly, 

 contributes to the striated appearance in sections, known collectively as the corpws 

 striatum (figs. 692, 695). The corpus striatum as such is described below. 



INTERNAL STRUCTURE OF THE PROSENCEPHALON 



From the above examinations of their external and ventricular surfaces, it is 

 apparent that the cerebral h(!misph(>res consist of a folded, external mantle of 

 grey substance, the cortex cerebri, spread more or less evenly over an internal mass 



