The descending cornu passes at first backwards and outwards 

 round the posterior part of the optic thalamus, then down- 

 wards, forwards and inwards. 



Relations : 



Roof. Floor. Inner Wall. Outer Wall. 



Fibres of corpus Hippocampus Pia mater. White substance 



callosum pass- major. of the hemi- 



ing to temporo- Tzenia hippocampi. sphere. 



sphenoidal lobe. Choroid plexus. 

 Amygdaloid tu- Eminentia collator- 



bercle. alis. 



Tail of caudate 



nucleus. 



The hippocampus major : a large white projection in the 

 whole length of the floor of the descending cornu. It corre- 

 sponds with the dentate sulcus. The anterior extremity 

 becomes enlarged and indentated, forming the pes hippocampi. 



Tcenia hippocampi or fimbria of the fornix : a narrow white 

 band prolonged from the posterior pillar of the fornix, and 

 lying along the inner margin of the hippocampus major. 



The septum lucidum is a double vertical partition between 

 the lateral ventricles, attached to the fornix and rostrum below, 

 and to the under surface of the body of the corpus callosum 

 above. Between the layers is the 5th ventricle, a closed 

 narrow space, having no connection with the other ventricles, 

 and not lined by ependyma. 



The fornix consists of two white longitudinal strata beneath 

 the corpus callosum, separated in front and behind, forming 

 the pillars, but joined in the middle, forming the body. 



The body is triangular in shape, the base being placed pos- 

 teriorly, and here connected with the corpus callosum. In 

 front of this it is connected with the septum lucidum along its 

 upper surface. The lateral margins are free, lying against the 

 choroid plexus of the lateral ventricles. The under surface 

 lies upon the velum interpositum. 



The anterior pillars pass downwards, forming the anterior 



