Corpus callosum-- -~~ 



THE LATEEAL VENTKICLE. 635 



objects may be recognised. From the lateral to the medial side these are met 

 in the following order : , (1) the caudate nucleus ; (2) a groove which extends 

 obliquely from before backwards and laterally between the caudate nucleus 

 and the thalamus, in which are placed the vena terminalis and a white band 

 called the stria terminalis ; (3) a portion of the superior surface of the thalamus ; 

 (4) the chorioid plexus; (5) the thin, sharp edge of the fornix (Fig. 564). 



The caudate nucleus narrows rapidly as it proceeds backwards on the lateral part 

 of the floor of the lateral ventricle. The vena terminalis (O.T. vein of the corpus 

 striatum) is covered over by ependyma. It joins the vena cerebri interna close to 

 the foramen interventriculare. The connexions of the stria terminalis will be dealt 

 with later. The portion of the superior surface of the thalamus which appears 

 in the floor of the ventricle is in great part hidden by the chorioid plexus, which 

 lies upon it. The lamina chorioidea is an epithelial fringe which is attached to 

 the sharp edge of the fornix superiorly and after surrounding a rich vascular 

 fold of pia mater becomes fixed to the superior surface of the thalamus. 

 The vascular fold is the chorioid plexus. In front it is continuous, in the inter- 

 ventricular foramen, with the corresponding chorioid plexus of the third ventricle 

 (Fig. 560), whilst behind, 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 must be borne in mind that it is invested by the epithelial 



Gyrus cinguli Indusium Stria longitudinalis medialis 



Commissura hippocampi^ { ^ ,/ m| ^xCavum septi pellucidi 



^/Septum pellucidum 

 5 ^.--Ventriculus lateralis 

 . -Grus fornicis 



^ _ J Plexus chorioideus 

 Nucleus caudatus ^H ZYfjfcl 2$S2^I 



- - - - Stria terminalis 



Tela chorioidea' "~ ~ ""^J^^Mf WfflJ^^HB^^T "^Attachment of lamina chorioidea 



-Thalamus (free surface) 



Thalamus / ; Tamia thalami 



Plexus chorioideus vent, tertii Ventriculus tertius 



FIG. 564. DIAGRAM OF TRANSVERSE SECTION ACROSS THE CENTRAL PARTS OF 

 THE LATERAL VENTRICLES. 



chorioidal lamina which represents a portion of the hemisphere wall and excludes 

 it from the cavity. 



Cornu Posterius. The posterior horn is an elongated diverticulum carried 

 backwards into the occipital lobe from the posterior end of the ventricle. It tapers 

 to a point and describes a gentle curve, the convexity of which is directed 

 laterally. The roof and lateral watt of this portion of the ventricular cavity are 

 formed by the tapetum of the corpus callosum. In frontal sections through the 

 occipital lobe this is seen as a thin but distinct layer of white fibres, which lies 

 immediately lateral to the ependyma and to the medial side of a much larger 

 strand of fibres in the medullary substance of the occipital lobe, viz., the optic 

 radiation. 



On the medial wall two elongated curved elevations may be observed. The 



uppermost of these is termed the bulb of the cornu (bulbus cornu posterioris), and is 



produced by the fibres of the radiation of the corpus callosum as they curve 



abruptly backwards from the lower part of the splenium of the corpus callosum into 



the occipital lobe. Below this is the elevation known as the calcar. It varies 



;reatly in size in different brains, and is caused by an infolding of the ventricular 



in correspondence with the anterior part of the calcarine sulcus on the 



irior of the hemisphere. It may come into contact with and adhere to the 



3ral wall of the ventricle in a part or even the whole of its extent. 



Cornu Inferius. The inferior horn is the continuation of the cavity into the 



smporal region. At first directed backwards and laterally, the inferior horn 



suddenly sinks downwards behind the thalamus into the temporal region, in the 



