CAPSULA INTERNA, CORPUS STRIATUM, INTERBRAIN-GANGLIA. 359 



appear to arise from the posterior parts of the capsula interna, perhaps from 

 the optic radiation. All pass into the depths of the thalamus, where they 

 collect into bundles between the thalamic ganglia, and thus apparently 

 separate these from one .another. Microscopic investigation shows that they 

 penetrate into the fine net-work of nerve-fibers which pervades these ganglia. 

 There may be distinguished in each thalamus: a mesial (inner) nucleus, 

 which projects into the ventricle; a lateral (outer) nucleus; and, between 

 these, the anterior nucleus. The lateral nucleus is the largest. The anterior 

 nucleus, with its blunt end directed anteriorly, appears as a wedge driven in 

 between the other two. This anterior, thicker end, which is visible an- 

 teriorly as an elevation on the surface of the thalamus, has been met with 

 earlier under the name of tuberculum anterius. 



The pulvinar borders on the mesial nucleus, and is not easily separable 

 from it in man. It is a huge "cushion" (Bolster) which, occupying the en- 

 tire posterior division of the thalamus, projects like a tumor {Wulst) into 

 the ventricle. On the median border of the inner nucleus lies the ganglion 

 hdbenulcB, previously mentioned. 



Monakow, who has recently studied the thalamic nuclei more thor- 

 oughly, proposes, on account of the structure and the entering radiations, 

 to separate the ventral region of the lateral nucleus and designate it, along 

 with several other small nuclei-groups which are also situated ventrally, as 

 the ventral nucleus of the thalamus. On the thalamus posteriorly there 

 lies, ventral and external to the pulvinar, a ganglion of a peculiar grayish 

 appearance: the corpus geniculatum later ale. It projects far into the sub- 

 stance of the thalamus, and gives origin to a large number of fibers of the 

 tractus opticus. 



Externally, the optic thalamus borders on the internal capsule (Fig. 

 160). Kumerous tracts, the corona radiata of the thalamus, pass from the 

 capsiile into the thalamus. They come from various directions and cross 

 one another as they converge into the thalamus. Masses of gray matter are 

 found within the net-work of crossing fibers. The outer zone, containing 

 these crossed fibers, is, from its appearance, designated as the "latticed" 

 layer (GitterschicM). Since most of the medullated fibers converge into the 

 lateral nucleus, this thus appears lighter than the other thalamic nuclei. 



The thalamic ganglia atrophy, to a large extent, if the cortical region 

 from which they receive their converging fibers degenerates or is removed. 

 The investigations by MonaJcow, especially directed toward these relations, 

 show that the most anterior and mesial divisions of the thalamus are con- 

 nected with the convolution-groups of the frontal lobe, the lateral nuclear 

 groups with the parietal convolutions, and the ventral nuclei with the 

 operculum. At present not the least is known concerning the physiological 

 significance of these pathways. Some of the other thalamic radiations are 



