246 



THE NERVOUS SYSTEM 

 THE LATERAL VENTRICLE 



When the corpus callosum and its radiation are cut away a cavity, known 

 as the lateral ventricle, is uncovered. It is lined by ependyma, continuous with 

 the ependymal lining of the third ventricle by way of the interventricular for- 

 amen. This cavity, which contains cerebrospinal fluid, varies in size in differ- 

 ent parts, and in some places is reduced to a mere cleft between closely apposed 

 walls. The shape of the ventricle is highly irregular (Fig. 176). As constit- 

 uent parts we recognize a central portion, anterior and inferior horns, and in 

 man also a posterior horn. The latter part develops rather late in the human 

 fetus as a diverticulum from the main cavity. 



Third ventricle 



Ant. horn 



[Lateral ventricle 

 Inf. horn) Central P art 



y Interventricular for. 

 ' " Optic recess 

 * ' Infundibulum 

 \ > Third ventricle 

 \^ Inf. horn 

 \^ Suprapineal recess 

 x Cerebral aqueduct 



Fourth ventricle 



Fourth ventricle 



Post, horn 



A B 



Fig. 176. Two views of the brain ventricles of man: A, Dorsal view; B, lateral view. 



The anterior horn, or cornu anterius, is the part which lies rostral to the 

 interventricular foramen. Its roof and rostral boundary are formed by the 

 corpus callosum. Its medial wall is vertical and is formed by the septum pellu- 

 cidum, which is stretched between the corpus callosum and the fornix (Figs. 

 177, 178). The sloping floor is at the same time the lateral wall, and is formed 

 by the head of the caudate nucleus, which bulges into the ventricle from the 

 ventrolateral side. In frontal section the cavity has a triangular outline; and 

 in such a section its walls and the relation which they bear to the rest of the brain 

 can be studied to advantage (Fig. 186). 



The central part or body of the lateral ventricle extends from the inter- 

 ventricular foramen to the splenium of the corpus callosum, where in man the 

 cavity bifurcates into posterior and inferior horns. The roof of the central 



