138 THE POCKET ANATOMY 



ovoid mass of grey matter lying outside and in front of the 

 optic thalamus. The largesfpart (lenticular nucleus) lies in the 

 white matter of the hemisphere outside the lateral ventricle, 

 and a smaller part (caudate nucleus) appears in the floor of that 

 space. 



The caudate nucleus is pear-shaped, with the larger end 

 placed anteriorly, occupying the floor and outer wall of the 

 anterior cornu ; the narrow posterior part lying along the floor 

 and outer wall of the lateral ventricle passes into the roof of 

 the descending cornu, where it is joined by the taenia semi- 

 circularis to form the amygdaloid tubercle. 



The lenticular nucleus lies outside and at a lower level than 

 the caudate nucleus, from which it is separated by a layer 

 of white fibres, the internal capsule. Outside the nucleus is 

 another stratum of white fibres, the external capsule, and 

 beyond this a thin lamina of grey matter called the claustrum, 

 the outer surface of which lies next to the white substance of 

 the island of Reil. 



The taenia semicircularis is a narrow band of white fibres 

 attached to the anterior pillar of the fornix in front, whence it 

 passes backwards in the floor of the lateral ventricle, between 

 the caudate nucleus and the optic thalamus ; it then passes 

 into the roof of the descending cornu, at the end of which it 

 enters a mass of grey matter, the nucleus amygdala, continuous 

 with the superficial grey matter at the apex of the temporo- 

 sphenoidal lobe, and placed just under the lenticular nucleus. 



The anterior commissure is a bundle of white fibres lying in 

 the anterior part of the 3rd ventricle, in front of the anterior 

 pillars of the fornix. The fibres go through the caudate 

 nucleus, and, passing under the lenticular nucleus, ultimately 

 enter the temporo-sphenoidal lobe. 



SYNOPSIS OF COURSE OF FIBRES IN THE CENTRAL 

 HEMISPHERES. 



i . Peduncular fibres, connecting cord and cerebellum with 

 cerebrum : 



(a) From crusta, chiefly through internal capsule to 



convolutions. 



(b) From tegmentum, chiefly to optic thalamus ; a part 



joins the inner capsule, and passes to occipital 



and temporo-sphenoidal lobes. 



The peduncular fibres, in their course to the convolutions, 

 are reinforced by fibres from the corpora striata and optic 

 thalami. 



