THE CEREBRAL GANGLIA* 491 



The Cerebral Ganglia. 



The corpora striata and optic thalami, from the position which they 

 occupy at the central part and base of the cerebrum, in the course of 

 the ascending fibres of the crura cerebri, must be regarded as nervous 

 centres interposed between the medulla oblongata below and the hemi- 

 spheres above. According to Henle, the bundles of white substance 

 from the posterior portion of the cms cerebri, on passing into the optic 

 thalamus, spread out in pencil-like tufts of diverging fibres, which become 

 generally distributed throughout the gray substance of the ganglion, 

 and are even mingled in its interior with transverse or interlacing fila- 

 ments. It is conceded by both Kolliker and Henle that some, or even a 

 considerable proportion, of these fibres terminate in the gray substance ; 

 while a portion, or perhaps other fibres originating in the gray substance, 

 pass outward again, from the anterior and lateral parts of the thalamus, 

 to continue their course upward to the cerebral convolutions. 



In the corpus striatum, the relation of the fibres to the gray substance 

 is, in general, the same as in the thalamus ; that is, they are derived 

 from the ascending bundles of the crus cerebri and terminate in the 

 gray substance of the ganglion. The difference between the two bodies 

 is that in the thalamus the mixture of the fibres with the gray substance 

 is more intimate and uniform throughout, while in the corpus striatum 

 the fibres are arranged in distinct bundles, readily visible to the naked 

 eye, which only disappear, by the dispersion and termination of their 

 filaments, at the distance of about one millimetre from its outer edge ; 

 so that the ganglion is bordered externally at this situation by a 

 thin layer of gray substance in which no white striations are to be 

 seen. In the corpus striatum, as in the optic thalamus, there are also 

 bundles of fibres, according to the observations of Kolliker, which at 

 certain levels pass from the gray matter of the ganglion into the white 

 substance of the hemispheres. Both the corpus striatum and optic 

 thalamus contain nerve cells with ramified prolongations, some of which 

 closely resemble the finest nerve fibres with which they are mingled, 

 and with which many anatomists believe them to be continuous. 



The exact physiological function of the cerebral ganglia, as distin- 

 guished from the hemispheres proper, is not precisely determined. It 

 is plain that they exert some influence, of an intermediate character, 

 between the action of the cerebral hemispheres above and the direct 

 transmission of motor and sensitive stimulus to or from the parts 

 below. They have both been found to be, like the hemispheres, insen- 

 sible to ordinary mechanical irritation, unless this be applied so deeply 

 as to reach the fibrous bundles of the crura cerebri in their inner and 

 deeper parts. They cannot be extirpated or extensively injured with- 

 out at the same time cutting off more or less completely the connection 

 of the hemispheres with the peripheral nervous system ; but they may 

 be removed at the same time with the hemispheres, in some of the lower 



