INTERIOR OF THE CEREBRAL HEMISPHERE 365 



teriorly but wider posteriorly in the rabbit, the cerebral 

 aqueduct (aquaeductus cerebri), which connects the third 

 ventricle with the fourth. 



(d) The corpus callosum is shown in section. Anteriorly it 

 appears to end in a somewhat club-shaped expansion, 

 though actually it is extended as a thin sheet of fibres 

 downward toward the lamina terminalis. Posteriorly it 

 bends downward, forming the splenium, the latter being 

 attached to the body of the fornix, which lies below it. 



The fornix consists of a pair of greatly curved longitudinal fibre- 

 bands, fused for a short distance in the middle line to form the unpaired 

 body of the fornix (corpus fornicis). They begin in the hippocampus 

 (p. 366) and end in the mamillary body, conveying to the latter 

 impulses resulting from the correlation of olfactory with other stimuli. 



(e) Between the body of the fornix and the anterior portion of 

 the corpus callosum is a thin area of the wall, the septum 

 pellucidum, the lateral ventricles approaching the medial 

 surface in each hemisphere and so lying close together in 

 this region. 



8. The cerebral cortex may be removed from part of one hemi- 

 sphere by carefully scraping away the grey matter over 

 most of the dorsal and lateral surfaces until the white 

 surface of the corpus callosum is well exposed. By removing 

 the corpus callosum, the interior of the hemisphere may 

 then be examined. 



(a) The lateral ventricle (ventriculus lateralis) is the extensive 

 cavity enclosed by the hemisphere. It reaches forward 

 into the olfactory bulb and backward into the posterior 

 free end of the hemisphere, passing a considerable distance 

 behind the opening of the interventricular foramen. 



(b) The excised portion of the hemisphere, forming the mod- 

 erately thick roof and dorsolateral wall, consists largely of 

 the superficial grey cortex. The extensive portion of the 

 hemisphere wall containing this cortex and the white matter 

 immediately under it is termed the pallium. 



