THE CEREBRUM. 



305 



These include: the two parts of the corpus striatum, the caudate and lenticular 

 nuclei, the clauslrum, the amygdaloid nucleus, and the thalamus. Of these, 

 two, the corpus striatum and the thalamus, will be briefly described. 



The Corpus Striatum. This large mass of gray matter, which 

 extends from the outer wall of the lateral ventricle to almost the cortex, 

 consists of two parts, the caudate nucleus or inner division and the lenticular 

 nucleus or outer division. Although continuous in front and below, the two 

 parts are separated almost completely by the intervening important tract of 

 white matter, the internal capstde, which is the great pathway for nerve- 

 fibres between the cerebral cortex and the lower portions of the brain. 



The caudate nucleus is an elongated comet-shaped mass of gray 

 matter, well seen from the lateral ventricle, and invested throughout the 



2=, 



F:G. 351. Portion of oblique frontal section of cerebrum, showing the ventricles, the basal ganglia 

 (caudate and lenticular nuclei and optic thalami) and the internal capsule, i, fornix, below corpus 

 callosum (25); 2, choroid plexus; 3, lateral ventricle; 4, stratum zonale ; 5, caudate nucleus; 6, internal 

 capsule, knee ; 7, mesial and (8) lateral nucleus of thalamus; 9, internal capsule; 10, putamen and (n) 

 globus pallidus of lenticular nucleus; 12, anterior pillars of fornix; 13, lamina terminalis; 14, anterior 

 commissure; 15, olfactory fibres; :6, thalamo-tegmental tract; 17, globus pallidus; 18, putamen; 19, 

 mammillo-thalamic tract; 20, external and (21) internal medullary lamina; 22, stria terminalis; 23, caudate 

 nucleus ; 24, striate vein ; 25, corpus callosum ; 26, cingulum ; 27, gyrus callosus. X j- (Preparation by 

 Professor Spiller.) 



greater part of its periphery by a dense layer of fibres, the stratum zonale, 

 covered on its ventricular surface by the cuboidal ependymal epithelium. The 

 nerve-cells of the nucleus are, for the most part, rather small pigmented and 

 stellate or fusiform and belong to type II, with short axones. Some cells, 

 however, are very large and provided with long axones which may pass into 

 the internal capsule. 



The lenticular nucleus lies to the outer side of the internal capsule 

 and is subdivided by two narrow tracts of white matter, the medullary 

 lamina, into three segments. Of these the outer one, \hz putamen, is the 

 darkest and corresponds in structure closely with the nucleus caudatus. 

 The middle and inner zones together constitute the globus pallidus and are 

 lighter in tint, owing to the excessive number of pervading bundles of nerve- 

 fibres. All three zones of the nucleus ienticularis consist of gray matter 



30 



