STRUCTURE OF THE CORPUS STRIATUM 207 



passing upwards from the crus cerebri, forming a white lamina termed 

 the internal capsule. Above the level of these nuclei the internal 

 capsule expands into the medullary centre of the hemisphere (see also 

 figs. 244 and 245, with their description). 



FIG. 243. FRONTAL SECTION THROUGH THE BRAIN AND SKULL MADE WHILST 



FUO/KN. 



c.c. corpus callosum ; below its middle part the septum lucidum, and below that again the 

 fornix ; L V, lateral ventricle ; Ih, thalamus ; between the two thalami the third ventricle 

 is seen ; below the thalamus is the subthalamic prolongation of the tegmental region, and 

 below this the prolongation of the crusta ; str, lenticular nucleus of the corpus striatum ; 

 c, caudate nucleus of the same ; between c, (h, and sfr, the internal capsule is seen ; outside 

 .<;/> is the thin grey band of the claustrum, and outside .this again the island of Reil at the 

 bottom of the Sylvian fissure ; n.a. nucleus amygdalae ; immediately within this is the optic 

 tract seen in section ; p, pituitary body ; B, body of the sphenoid bone ; sa, subaracbnoid 

 space ; r, villi of the arachnoid. 



The nucleus caudatus of the corpus striatum is composed of a 

 reddish-grey neuroglia containing both moderately large and small multi- 

 polar nerve-cells. It receives fibres from the part of the internal 

 capsule which separates it from the nucleus lenticularis, and next the 

 lateral ventricle it is covered by a thin layer of neuroglia, and over 

 this by the epithelium of the cavity. 



The nucleus lenticularis, which corresponds in position internally 

 with the island of Reil externally, is divided by two white laminag into 

 ihree zones. It is separated from the nucleus caudatus and optic thala- 

 mus by the internal capsule (figs. 244, 245, ic], which consists of the 

 bundles of medullary fibres which are passing between the white centre 

 of the hemisphere and the crus cerebri ; it receives on its inner side 

 many white fibres from the capsule, and these impart to it a radially 

 striated aspect. Many of the nerve-cells of the nucleus lenticularis 

 contain yellow pigment. 



