THE NERVOUS SYSTEM 



1407 



and a floor. The roof is formed by the corpus callosum (tapetum). 

 The inner wall is formed by the posterior part of the septum lucidum, 

 and, behind this, by the attachment of the body of the fornix to 

 the under surface of the corpus callosum. Externally the body is 

 limited by the meeting of the roof and floor. The floor presents 

 the following structures, in order from within outwards : (i) the 

 sharp lateral border of the fornix ; (2) the choroid plexus of the 

 lateral ventricle ; (3) a portion of the upper surface of the optic 

 thalamus ; (4) an oblique groove, extending forwards and inwards 



Third Ventricle 



^,« Anterior Comu 



Descending C(»iia 



-Suprapineal Recess 



Fotuth Ventricle 



Lateral Recess of 



Fourth Ventricle 



Impression for Bulbus 

 Comu Posterioris 



Posterior Comu 



Fig. 592. — Drawing of a Metal Cast of the Ventricles of the 

 Brain of an Adult (Superior View) (Retzius). 



between the optic thalamus and nucleus caudatus, in which 

 there are (a) a white band, called the taenia semicircularis, and 

 (b) the vein of the corpus striatum, the latter being the more super- 

 ficial of the two ; and (5) the narrow part of the nucleus caudatus 

 of the corpus striatum. 



The anterior cornu has its roof formed by the corpus callosum 

 (forceps minor}. Externally it is limited by the meeting of the 

 roof and floor. Anteriorly where it is pointed, it is bounded by 

 part of the posterior aspect of the genu of the corpus callosum. 

 Its inner wall is formed iDy the anterior part of the septum lucidum. 



