DISSECTION OF THE BRAIN. 83 



Note its extensive cotu^se, sweeping around ciownivai'd 

 and forzuard to the bottom of the temporal lobe of the 

 hemisphere. 



f. The Hippocampus Major is the prominent con- 

 vex ridge lying along the floor of the descending 

 cornu. 



g. The Fornix. T\\t posterior pillar of the fornix 

 is the narrow band of white fibres lying along the 

 anterior border of the hippocampus major. The pos- 

 terior pillars on each side followed forward meet just 

 at the posterior edge of the septum lucidum, and unite 

 for a short distance to form the body of the fornix ; 

 then bending downward they diverge again, forming 

 the anterior pillars of the fornix, which run toward 

 the base of the brain. 



Ciit aivay the outer ivall of the anterior cornn on 

 the sajne side on zuhich the zuall of the posterior cornn 

 was removed. 



h. The Foramen of Monro, one on each side, is 

 the slit-like opening underneath the body and anterior 

 pillar of the fornix. It leads into the 3d ventricle, 

 and is the passage of communication between the 3d 

 and the lateral ventricles. 



To expose the 2id ventricle lift 7ip carefully the pos- 

 terior pillars of the fornix zvhcre they co7iverge and 

 tear tJiem azuay with the forceps Remove in the same 

 way the portion of the corp^is callosnm still left be- 

 tween the posterior pillars of the fornix and forming 

 the roof of the 3c/ ventricle. 



Properly speaking, the corpus callosum does not 

 form the roof of the 3d ventricle. The true roof of 

 the ventricle is a portion of the pia mater known as 

 the vehtm interpositum which lies immediately be- 

 neath the corpus callosum. The velum interpositum 



