THE CEREBRUM 



429 



must be removed to give a view of the cavity. The dissection 

 necessitates the removal of the temporal operculum, but the 

 surface of the insula should be preserved from injury. 1 



.Lateral Ventricle. When the dissection is completed, 

 the dissector cannot fail to note that each cerebral hemisphere 

 is hollow. The cavity in the interior is called the lateral 

 ventricle. It is lined with a thin dark -coloured layer of 

 epithelium which is termed the ependyma. In certain places 

 its walls are in apposition with each other, but in other 



Central part of lateral ventricle 



Pineal recess 



Supra-pineal recess 

 Aquaeductus 

 cerebri 



Fourth 

 ventricle^ 



Interventricular 

 > x foramen 



Third ventricle 

 'Optic recess 



Infundibular recess 



Inferior horn 



Lateral recess 



FIG. 165. Cast of the Ventricles of the Brain. (From Retzius. ) 



localities spaces of varying capacity, and containing cerebro- 

 spinal fluid, are left between the boundary walls. The lateral 

 ventricle communicates with the third ventricle of the brain 

 by means of a small foramen which is termed the inter- 

 ventricular foramen (O.T. foramen of Monro) (Figs. 160, 165). 

 That aperture, which is just large enough to admit a crow- 

 quill, lies at the anterior end of the thalamus, and posterior to 

 the column of the fornix (O.T. anterior pillar). To find the 

 aperture, the dissector should note the rough fringe of vascular 

 pia mater which lies on the floor of the ventricle, and he should 

 follow the fringe forwards to its passage into the foramen. 

 The shape of the lateral ventricle is very irregular, but it 



1 If the hemispheres have already been separated from one another the 

 dissection must be carried out on each side separately. 



