BASAL GANGLIA 467 



sections in their proper relations to each other at one time, 

 and separate them from each other again, when necessary, 

 and so confirm the majority of the statements contained in 

 the following accounts of the individual- structures. 



Corpus Striatum. The corpus striatum is a mass of grey 

 matter embedded in the base of the hemisphere. It consists 

 of two parts a supero-medial part, the caudate nucleus, and 

 an infero-lateral part, the lentiform nucleus. The anterior 

 portions of the two nuclei are blended together, but the 

 remaining portions are separated from one another by a thick 

 layer of white substance of the hemisphere, called the internal 

 capsule. 



Nucleus Caudatus. The caudate nucleus is a comma- 

 shaped mass. The head of the comma lies in tKe lateral 

 wall of the anterior horn of the lateral ventricle. The 

 body runs backwards, in the lateral part of the floor of the 

 central portion of the cavity of the lateral ventricle and the 

 tail turns downwards and forwards in the roof of the inferior 

 horn. The lower and anterior part of the head is fused with 

 the anterior part of the lentiform nucleus (Fig. 185). One* 

 surface of the caudate nucleus is intravehtricular, that is, it is 

 in direct relation with the cavity of the lateral ventricle and is 

 covered with the 'ependyma. The opposite surface is extra- 

 ventricular. The extraventricular surface of that part of the 

 nucleus which lies in the anterior horn, and in the central 

 part of the lateral ventricle, is in relation with the internal 

 capsule, but the extraventricular surface of the portion of the 

 tail which lies in the roof of the inferior horn of the ventricle 

 is separated from the lower surface of the lentiform nucleus 

 by fibres passing, more or less transversely, between the 

 cortex of the temporal lobe and the upper part of the corre- 

 sponding peduncle of the brain and the subthalamic region. 

 The medial border of the caudate nucleus is separated from 

 the thalamus by the stria terminalis ; and the lateral border, 

 in the region of the anterior horn and the central part of the 

 lateral ventricle, is in relation- with the medial surface of the 

 upper part of the internal capsule, and with a bundle of 

 longitudinal fibres of the white matter of the cerebrum called 

 the occipito-frontal fasciculus (Fig. 1 88). 



Nucleus Lentiformis. The lentiform 'nucleus is an 

 irregular triangular pyramid of grey matter. It possesses an 

 inferior surface or base (Figs, i&y, 188); a lateral surface; 



