THE BRAIN 135 



than at the middle, and thickest behind. It terminates pos- 

 teriorly in a free, thickened border, the splenium ; in front it 

 curves down towards the base of the brain, the bend being 

 known as the genu, and the reflected part as the rostrum. 



Raphe : the longitudinal eminence along the centre of the 

 upper surface. 



Nerves of Lancisi (striae longitudinales) : longitudinal white 

 fibres placed on each side of the raphe. 



Covered band of Reil : longitudinal fibres outside the nerves 

 of Lancisi, under cover of the convolution of the corpus 

 callosum. 



Relations. Upper surface forms floor of great longitudinal 

 fissure ; under surface connected behind with the fornix, and 

 in front of this with the septum lucidum. The extremity of the 

 rostrum is connected centrally with the lamina cinerea, and 

 laterally with two white bands, the peduncles of the corpus 

 callosum, which pass backwards and outwards over the anterior 

 perforated spot towards the Sylvian fissure to the anterior 

 extremity of the temporal lobes. Traced upwards, these 

 fibres are continuous with nerves of Lancisi The corpus 

 callosum roofs in the bodies and anterior cornua of the lateral 

 ventricles. 



The lateral ventricles are two in number, one in each 

 hemisphere. They communicate below and in front with 

 one another and with the 3rd ventricle by the foramen of 

 Munro. Each ventricle consists of a body or central cavity, 

 and three cornua, anterior, posterior, and descending. 



Relations of the body : 

 Roof. Corpus callosum. 



Internal wall. Septum lucidum and the fornix. 

 Floor. From before backwards. 



1. Caudate nucleus of corpus striatum. 



2. Tasnia semicircularis. 



3. Part of optic thalamus in front of choroid plexus. 



4. Choroid plexus of lateral ventricle. 



5. Fimbriated edge of the fornix. 



The anterior cornu is the anterior end of the ventricle which 

 curves outwards round the caudate nucleus. 

 Relations : 



In Front. Roof. Floor and Externally. Internally 



Genu of corpus Corpus callosum. Caudate nucleus. Septum 1 

 callosum. dum. 



The posterior cornu projects backwards and inwards into tfc 

 occipital lobe. 



