VII] 



Lhiibic Lobe <(ti(f Olfactory Area- 



1 sf, 



Topical Variations. 



This may be taken as describing the general type of fibre-arrangement in the cortex 

 of the gyrus fornicatus, but certain topical variations must here be referred to. It may 

 be noticed as \ve proceed backwards that after the middle of the convolution is passed 

 there begins a pronounced general increase in the fibre-wealth ; at first the increase is 

 confined to the cortex immediately overlying the corpus callosum, but the strip gradually 

 widens, until behind the splenium it attains a breadth of 5 to 10 mm. (vide Plate I. C). 



Flo. 18. Radiary zone in the cortex of the gyrus fornicatus. xifs. 

 Coincident with the small size of the resident nerve cells the nerve fibres are fine. 



Concerning individual elements there are no differences to record between this strip and 

 the rest of the area, the fibres remain small in calibre and wavy in outline, and are only 

 greatly increased in number. One point, however, deserves special recognition : it is that in the 

 curt ex in contact with the corpus callosum that is the cortex of the callosal fissure the 

 zonal layer is so dense and prominent that it resembles the lamina medullaris externa of 

 the hippocampal region, and it tails off in a similar way as it passes outwards. As the 

 diagram shows, the part exhibiting this formation is coterminous posteriorly with the subicular 

 hippocampal region already described. 



c. 24 



