768 



DISSECTION OF THE BRAIN. 



globus 

 pallidus 

 maj or and 

 minor. 



Internal 

 capsule, 



parts, 



source of 

 fibres ; 



parts the globus pallidus major and minor. The three parts are 

 concentrically disposed from without inwards, and faint white lines 

 indicate the separation between them. 



The INTERNAL CAPSULE (figs. 278 and 279) is a thick layer of 

 white fibres, which is seen in the horizontal section to form a bend, 

 or genUj (fig. 278, icg), opposite the groove between the optic 

 thalamus and the head of the caudate nucleus. The part in front 

 of the genu is named the anterior limb (ica), and the longer part 

 behind is the posterior limb (icp) of the capsule. The internal 

 capsule is formed in large part by the fibres of the crusta of the 

 crus cerebri coursing upwards to the medullary centre of the hemi- 

 sphere, but many fibres are added from the nuclei on each side. 



corp 



.call 



Ictfc. vcn-t. 

 st>t. lu,c 



opt. tnal 



ant. eomm.. 



int. caps 



opt. tract. - 



coi'p.all) 



infunaib 



ectue}. nu,ci. 

 tccnia.aemic 



tent. nucl. 

 insula 



(.laustrunv. 



amyxjci. nucl. 



FIG. 279. CORONAL SECTION OF THE CEREBRUM, PASSING THROUGH THE FORE 

 PART OF THE THIRD VENTRICLE. THE ANTERIOR POSITION is REPRE- 

 SENTED (AFTER MERKEL). 



pyramidal 

 tract. 



The pyramidal fibres, which have been traced from the medulla 

 oblongata through the pons, and crusta, occupy the anterior two- 

 thirds of the posterior limb. The posterior third of the posterior 

 limb contains a few fibres that pass directly from the tegmentum, 

 others which pass from the grey matter of the thalamus and, 

 most posteriorly, fibres radiating the optic radiation to the 

 angular and cuneate convolutions from the lower visual centres 

 contained in the pulvinar of the optic thalamus, the external 

 geniculate body and the. anterior corpus quadrigeminum. 

 The anterior limb contains fibres which are connected with the 

 grey matter of the head of the caudate nucleus and the cortex of 

 the frontal lobe. The fibres of the capsule are collected into 



