P. CALLOSUM 



ANT? LIMB 

 INT 1 : CAPSULE 



STRUCTURAL ARRANGEMENTS OF CEREBRUM 423 



the outer part of the pulvinar and the external geniculate body and constitute 

 the so-called ' optic radiation/ passing outwards and backwards to be 

 distributed to the cortex of the occipital lobe. The ventral fibres pass 

 downwards and outwards below the lenticular nucleus and end partly in the 

 latter nucleus and partly in the cortex of the temporal lobe and of the insula 

 or island of Reil. 



(2) THE FILLET SYSTEM OF FIBRES. This great mass of ascending fibres 

 has been already described (cp. Fig. 197) as gathering up the impulses 

 from the different sensory 



nerves of the cerebro-spinal 

 system and terminating in the 

 thalamus and subthalamic 

 region. 



(3) THE SUPERIOR CERE- 



BELLAR PEDUNCLE. These 



fibres, from the central 

 ganglia of the cerebellum, 

 terminate for the most part 

 in the thalamus and sub- 

 thalamic region. It is pos- 

 sible that some of them may 

 pass through the hinder end 

 of the internal capsule, with- 

 out interruption in the thala- 

 mus, to end in the Rolandic 

 area. 



(4) THE OPTIC RADIATION. 

 These diverging fibres in the 

 back part of the corona- 

 radiata are mixed up with 

 fibres which are partly cortici- 

 fugal. The corticipetal fibres 

 arise in the pulvinar and the 

 external geniculate body and 

 end in the occipital cortex. 



(5) THE AUDITORY RADIATION. These fibres consist of the axons of cells 

 situated in the internal geniculate body. They pass through the posterior 

 limb of the internal capsule under the lenticular nucleus to end in the 

 temporal lobe. 



B. THE EFFERENT PROJECTION FIBRES. . 



(1) THE PYRAMIDAL TRACT. This is composed of fibres which arise from 

 the large Betz cells in the ascending frontal convolution, the ' motor area.' 

 They pass through the corona radiata into the internal capsule, where they 

 occupy the genu and the anterior two-thirds of the posterior limb, 

 they pass into the crusta, where they occupy the middle two-fifths of this 



CORP: GEN : INT. 



SUP QUADS BODY 



TEMPORO-PONTINE 

 TRACT 



LOBE. 



FIG. 214. Schema of projection fibres of cortex- 

 (CUNNINGHAM.) 



