Ill 



of Arrangement of Nerve A T /Yi>rx 



25 



fibres, meets tin- case. Thus, exammat ,1011 shows that from the summits of the radiary pro- 

 |eetioiis downwards, the enrte\ is so eojiiallv iiuil richly stocked with fibres, that it is almost 

 impossible to break it up into laminae ; one can merely say that at or towards the upper 

 extremity of the radiating fasciculi, the plexus seems to be especially rich in small fibres. 

 Towards the anterior wall of the convolution, on the other hand, where the type of arrangement 

 assumes an intermediate character and the iuterradiarv elements become less numerous, a line 

 of Baillarger gains in distinctness. 



Radiations of Meynert : Interradiary Plexus and Association Fibres. 



Although the rich supply of fibres in the zonal layer and supraracliary field is a striking 

 feature, it is the extraordinary development of the fibre constituents in the deeper levels 

 which above all gives character to the precentral cortex. Not only is the process of white 

 substance which forms a foundation for the cortex and from which the bundles of projection 



v: 



Fio. 1. The radiary zone in the precentral cortex, . ';". 



The extraordinary fibre wealth comes out very plainly in a high power drawing. Numbers of fibres of large calibre 

 are seen both in the radiary bundles and crossing the interradiary spaces. It must be remembered that the 

 portion drawn is about on a level with the giant cells of Betz. Compare with the drawing of the post-central 

 cortex, text figure 5. The fine wavy elements in the radiations and intervening parts are common constituents 

 to be seen in any part of the brain. 



C. 



4 



