THE CORPUS STKIATUM. 



135 



nucleus is continuous below with the superficial grey matter forming the anterior 

 perforated lamina, into which the base of the claustrum also passes, and further 

 back it comes in contact below with the nucleus amygdalae (fig. 98) ; through 

 these structures it is continuous with the grey cortex of the hemisphere. 



All three zones of the nucleus lenticularis are pervaded by bundles of white fibres, 

 but they are most conspicuous in the outer zone. The grey matter between the fibres 

 contains many cells with yellow pigment in them. The cells on the whole resemble 

 those of the caudate nucleus, but there are more in proportion belonging to the first 

 type of Golgi (cells with a long nerve-process). Fibres pass directly from the 

 inner zone into the adjacent part of the inner capsule (i.e., into the peduncle of the 

 cerebrum), while others from the substantia innominata below the optic thalamus. 



Fig. 99. HORIZONTAL SECTION THROUGH PART OP 



THE CEREBRAL HEMISPHERE. (E. A. S. , after a 



preparation by Mr. S. G. Shattock.) Natural size. 1 



The section is viewed from below ; v.l, lateral 

 ventricle, anterior cornu ; c.c, corpus callosum ; 

 s.l, septum lucidum ; ../, anterior pillars of the 

 fornix ; v 3, third ventricle ; th, thalamus opticus ; 

 st, stria terminalis ; c, nucleus caudatus, and n.l, 

 nucleus lenticularis of the corpus striatum ; i. c, in- 

 ternal capsule ; g, its angle or genii ; n.c, tail of the 

 nucleus caudatus appearing in the descending cornu 

 of the lateral ventricle ; cl, claustrum ; /, island of 

 Reil. 



curve outwards around the mesial edge of 

 the peduncle and enter the lower part of 

 the lenticular nucleus as a distinct bundle 

 (ansa lenticularis, p. 112) and passing into 

 its medullary laminae are distributed in the 

 middle and outer zones. 



Other fibres connect the caudate with 

 the lenticular nucleus, and others again pass 

 from this nucleus into the corona radiata 

 or white substance of the hemispheres and 

 thence to the cortex, but few fibres emerge 

 from or enter the lateral surface of the 

 lenticular nucleus, which is sharply marked i__ 

 off from the external capsule. 



The external capsule is formed of fibres which are not directly connected with 

 the lenticular nucleus but are derived partly from the anterior commissure, and in 

 part from a portion of the ansa lenticularis. 



The claustrum (figs. 96 to 100, cl) is a thin lamina of grey matter which is smooth 

 next to the outer capsule but ridged and furrowed externally, the ridges and furrows 

 corresponding to the gyri and sulci of the central lobe, with the white substance of 

 which the claustrum is in immediate relation. According to Meynert the claustrum 

 is to be looked upon as a separated part of the grey cortex of the central lobe. In 

 transverse sections of the hemisphere the claustrum is seen to taper to a fine thread 

 superiorly (apex) and to expand below (base), having the shape of an elongated 

 triangle. 



In the claustrum the cells are for the most part small and spindle-shaped, and 

 arranged parallel with the surface, resembling those which are met with in the 



1 This figure shows the narrowed connections of the island of Reil with the rest of the hemisphere 

 (mantle). These narrow connecting parts have been termed by Gruldberg isthmi (anterior et posterior) 

 lobi centralis. 



