210 



Tt/pe of Arrangement of Nerve Fibres 



[CHAP. 



the " precentral " area proper and worse along the anterior margin : in other words, it shows 

 a gradual falling off from behind forwards. 



Supraradiary Layer. 



Compared with the same layer in the " precentral " area, this is poorly supplied with 

 nerve fibres, the difference being specially noticed at the level corresponding with the second 

 layer of nerve cells (small pyramids). The field is occupied mainly by fine short fibres, lying 

 in all directions but mostly having a transverse trend. An occasional ascending fibre of 

 Martinotti stands out on account of its larger calibre; and in the lower parts, where the fibre- 

 wealth increases, long transverse fibres of medium size, which probably belong to the association 

 system, are recognised. 



Fio. 21. The radiary zone in the intermediate precentral cortex at a magnification of if 1 . 



Compared with the corresponding drawing from the precentral area, figure 1. page 25, a great reduction in number 

 of large medullated fibres will be noticed ; some of these fibres are however still present in the radiating 

 fasciculi and iuterradiary plexus, but tine wavy varicose fibres predominate. 



Tlie Line of Baillarger. 



Although its upper and lower boundaries defy accurate definition, yet the line is well 

 represented and is of great breadth. Its principal constituents are short, delicate, transverse 

 fibres, but some long, medium-sized, non-varicose members give prominence to the band. 



