434 



THE BRAIN 



downwards and disappears from view in the region of the 

 interventricular foramen. Its fibres ultimately reach the 

 substantia perforata anterior, in which they end. 



The portion of the upper surface of the thalamus which 

 appears in the floor of the lateral ventricle is, in great part, 

 overlaid by the chorioid plexus of the lateral ventricle. The 

 plexus is a rich vascular fringe which appears from under 

 cover of the sharp edge of the fornix. It is continuous 

 anteriorly, through the interventricular foramen, with the 

 corresponding chorioid plexus of the opposite side ; whilst 



Bulb of cornu 



Splenium 



Bulb of corni 



Calcar avis 



\ Tapetum 

 \ \ 

 \ Optic radiation 



Inferior longitudinal bundle 



FIG. 169. Frontal section through the Posterior Horns of the 

 Lateral Ventricles. 



posteriorly, it is carried into the inferior horn of the ventricle. 

 Although the chorioid plexus has all the appearance of lying 

 free within the ventricle, it is invested by an epithelial layer 

 of ependyma, which excludes it from the cavity and is 

 continuous on the one hand with the ependyma on the 

 sharp margin of the fornix, and on the other with the 

 ependyma of the upper surface of the thalamus. 



Cornu Posterius Ventriculi Lateralis. The posterior 

 horn is a diverticulum which runs, from the posterior end of the 

 central part of the ventricle, into the occipital lobe. It tapers 

 to a point and describes a gentle curve, the convexity of 

 which is directed laterally. The roof and the lateral wall of 



