1 172 HUMAN ANATOMY. 



The Connections of the Corpus Striatum. — Much uncertainty prevails as to the details of 

 the connections of the several parts of the corpus striatum and little is known regarding the 

 function of these nuclei, notwithstanding their size ; certain general principles, however, may be 

 accepted as established. The comparative studies of Gehuchten, Sala and others, and especially 

 of Edinger, emphasize that the corpus striatum is to be considered as supplemental to the 

 cortical substance, in the lower vertebrates in which the cortex of the cerebral mantle is feebly 

 developed constituting the chief mass of cortical gray matter, and in the mammals and man 

 being subservient to the overshadowing cortex of the hemisphere. Such being the warranted 

 presumption, it is to be anticipated that the striate body both receives fibres conveying sensory 

 impulses and gives off fibres (perhaps motor in function) originating from its cells, these latter 

 tracts constituting the strio-thalamic radiation. 



The centripetal or afferent paths probably include : ( i ) the tegmento-striate fibres, which 

 are continued chiefly from the mesial fillet, and perhaps also from the red nucleus and subthal- 

 amic region, by way of the internal capsule, to end around the cells of the putamen and head of 

 the caudate nucleus ; (2) the thalamostriate fibres, already mentioned in connection with the 

 thalamus (page 1 123), which pass from the thalamus either by way of the internal capsule directly 

 to the caudate nucleus, or by way of the ansa lenticularis to the putamen or, traversing 

 the medullary laminae, to the catidate nucleus. No doubt many of the fibres which enter the 

 lenticular nucleus do not end within the latter, but traverse its substance as part of their path to 

 the cerebral cortex. 



The centrifugal, or efferent fibres, which arise from the cells of the corpus striatum include : 

 (i) the strio-thalauiic fibres, passing from the major divisions of the striate body, which 

 comprise [a) those from the caudate nucleus to the thalamus direct ; {b) those which traverse 

 the internal capsule and the medullary laminae and, joining fibres from the putamen, pass by 

 way of the ansa lenticularis to the thalamus ; [c) those from the putamen which reach the 

 thalamus by passing partly by way of the globus pallidus and partly, in greater numbers, by 

 means of the ansa lenticularis. (2) Strio-peduncular fibres, well represented in the brains 

 of the lower animals as the continuation of the basal tract of the fore-brain (Edinger), which 

 pass from the caudate nucleus, and probably from the lenticular nucleus also, into the 

 sub-thalamic region and the cerebral peduncle, within the latter forming the stratimi inter- 

 medium closely related to the substantia nigra. Whether cortico-striate fibres, e.xtending 

 from the cerebral cortex to the corpus striatum, exist in man is uncertain, Dejerine denying 

 their presence, whilst Edinger regards the presence of a meagre number of such bundles 

 as established. 



The Claustrum. — The claustrum is a thin lamina of gray substance embedded 

 within the white matter intervening between the lateral surface of the putamen and 

 the cortex of the island of Reil. Its mesial surface is smooth and parallel with the • 

 outer aspect of the putamen, from which it is separated by the thin tract of white 

 matter constituting the external capsule. Its lateral surface presents a series of 

 elevations and depressions which in a general way repeat the contour of the gray 

 cortical lamina of the insula, the intervening layer of white matter being sometimes 

 called the capsula extrema. Seen in horizontal sections (Fig. loii), the claustrum 

 fades away both in front and behind ; in frontal sections (Fig. loio), however, whilst 

 it graduahy disappears above, below the claustrum materially thickens and mesially 

 becomes continuous with the anterior perforated substance. Upon comparative and 

 developmental grounds, the claustrum must be regarded as a separated portion of 

 the corpus striatum. Its nerve-cells are, for the most part, small and either stellate 

 or fusiform in outline. Nothing is known with certainty as to the course or connection 

 of its fibres. 



The Amygdaloid Nucleus. — This structure (nucleus amygdalae) comprises 

 a considerable rounded mass of gray substance (Fig. lOio) which occupies the 

 fore-part of the temporal lobe and lies in close proximity with the uncus, overlying 

 the extremit}' of the inferior horn of the lateral ventricle. Anteriorly it is continuous 

 with the cortical gray matter of the temporal lobe as a thickened portion of which 

 it may be regarded. Its lower part receives the tail of the caudate nucleus and 

 close to this, the taenia semicircularis (page 1162), which accompanies the recurved 

 nuclear tail in its descent within the roof of the inferior horn. The nucleus 

 approaches, if indeed it does not touch, the anterior perforated substance, and above 

 comes into intimate relations with the lenticular nucleus. It is highly probable that 

 the nucleus amygdalae forms, along with the uncus and the hippocampus, a part 

 of the olfactory cortex (Dejerine). 



