BASAL GANGLIA OF THE CEREBKAL HEMISPHEEE. 



641 



the lentiform nucleus into the caudate nucleus (fibrse lenticulocaudatse). From the 

 globus pallidus fibres arise which proceed into the internal capsule in the region of the 

 genu and the neighbouring part 

 of the posterior limb (Fig. 572). 

 Many of these fibres become 

 collected on the inferior aspect 

 of the lentiform nucleus, where 

 they form a transversely directed 

 bundle (Fig. 570), known as the 

 ansa lenticularis, which is dis- 

 tributed to the thalamus (Fig. 

 571, fasciculus striothalamicus) 

 and hypothalamus, the red 

 nucleus (fasciculus striorubricus) 

 and substantia niger (fasciculus 



Red nucleus 



Thalamus 



Substantia 

 nigra 



Rubrospinal 

 tract 



FIG. 571. 



Internal capsule 



-Claustrum 



Insula 



__- Putamen 



Globus 

 pallidus 



Motor 

 trigeminal 



Ansa peduncular^ 



Nucleus amyadalae 



nucleus 

 AGRAM OP A FRONTAL SECTION TO ILLUSTRATE THE 



FIBRE CONNEXIONS OF THE CORPUS STRIATUM. 



strionigricus). These connexions 

 afford some explanation of the 

 difficulties of articulation and 

 swallowing and in the perform- 

 ance of delicate voluntary move- 

 ments that result from damage 

 to the corpus striatum or to this 

 system of fibres. 



This system of fibres is phylo- 

 genetically very old, being the 

 most primitive efferent tract from the cerebral hemisphere. 



Claustrum. This is a thin plate of gray substance embedded in the white 

 matter which intervenes between the lentiform nucleus and the gray cortex of 

 the insula. Followed in an upward direction, it becomes gradually thinner and 

 ultimately disappears. As it is traced downwards, however, it thickens consider- 

 ably, and at the base 

 of the brain it comes 

 to the surface at the 

 anterior perforated 

 y^v.-/.-v\A - substance and becomes 



Flbrae corricosfriarae 



, -Fasciculus fronroponhcus. 



Fibrae 



f. \\Vlenriculocaudarae. 

 (V Anterior thalamic 



radiarion 

 -7 



Cenu 

 capsulte 



inrernae 



To oculomotor iiuc 



To facial, trigeminal, vagal, 

 and hypoglossal nuclei 



continuous with 

 gray matter of 



the 

 the 



cortex. Its extent 

 corresponds very 

 closely with the area 

 occupied by the insula, 

 and its surface towards 

 this portion of the 

 cerebral cortex shows 

 ridges and depressions 

 corresponding to the 

 Auditory radiarion, ^sular gyri and sulci. 

 Nucleus Amyg- 

 dalae. In the anterior 

 p ar O f ^ e temporal 

 region, above the piri- 

 form area a fusiform 

 mass of gray matter 

 appears upon the sur- 

 face (Fig. 558, p. 630), 

 at the lateral extremity of the substantia perforata anterior (Fig. 584, p. 657). It 

 is part of a large rounded mass, called the amygdaloid nucleus, which occupies a 

 position in front of, and to some extent above the extremity of the inferior 

 horn of the lateral ventricle. The tail of the caudate nucleus joins its inferior part 

 (Fig. 573, p. 643), whilst above it is carried up into the putamen (Fig. 570). 



42 



Thalamo-cerebral tract to 

 posterior central gyms 



Thalamo-cerebral tract to supra - 

 marginal and angular gyri 



Opric radiarion. 



caudate nucleus 



FIG. 572. DIAGRAMMATIC REPRESENTATION OP THE INTERNAL CAPSULE 

 (AS SEEN IN HORIZONTAL SECTION). 



