THE LATERAL VENTRICLES 



875 



The central portion or body is more nearly horizontal. It lies within the 

 parietal lobe and extends from the interventricular foramen to the level of the 

 splenium of the corpus callosum. Its roof is formed by the inferior surface of the 

 bod}'' of the corpus callosum, and its mesial wall consists of the posterior part of 

 the septum pellucidum, attaching the fornix to the under surface of the corpus 

 callosum. Like the anterior horn, it is given an oblique, infero-lateral wall by 

 the narrower, middle part of the caudate nucleus. Several structures contribute 

 to its floor: — (1) the stria terminalis of the thalamus, a line of white substance 

 conforming to the genu of the internal capsule without, and constituting the 



Fig. 688. — Horizontal Dissection 'of the Cerebral, Hemispheres. 

 The fornix has been removed to show the relation of the tela chorioidea of the third ventricle to 

 the chorioid plexus of the lateral ventricles. (From a mounted specimen in the Anatomical 

 Department of Trinity College, Dublin.) 



Veins of Galen 



Cms of £omix 



Straight sinus 



Cerebellum 



Stria termin- 

 alis of thala- 

 mus 



Thalamus 



Tela chori- 

 oidea 'velum 

 interpositum) 



Chorioid 



I plexus 

 n Fimbria 



-.^\ Hippocampus 



J ) major 



J ^'-Collateral 



eminence 



Hippocampus 



minor 



boundary between the caudate nucleus and the thalamus, and containing (2) the 

 vena terminalis (vein of the corpus striatum); (3) the lamina affixa, a mesial 

 continuation of the stria terminalis upon the surface of (4) the lateral part of the 

 thalamus; (5) the medial edge of the lamina affixa, the taenia chorioidea, and the 

 chorioid plexus continuing under (6) the edge (tsenia) of the body and the begin- 

 ning crura (posterior pillars) of the fornix (fig. 688). 



The chorioid plexus of the lateral ventricle is continuous with that of the third 

 ventricle. The chorioid tela of the third ventricle (velum interpositum) con- 

 tinues under the tsenia of the fornix into the lateral ventricle, and there, along the 

 line of the taenia chorioidea, becomes elaborated into a varicose, convoluted, 

 villus-like fringe, rich in venous capillaries and lymphatics. This fringe is the 

 chorioid plexus. It is continuous anteriorly, at the interventricular foramen, with 

 the corresponding plexus of the opposite lateral ventricle and with the chorioid 

 plexus of the third ventricle. The latter consists of two similar but smaller 

 fringes, which project close together into the cavity of the third ventricle from the 

 median portion of the ventral surface of the chorioid tela. Behind, the chorioid 



