178 



Struct tire of the Lobus Pi/rifonnis 



[CHAP. 



fibres pierce the line of Baillarger and snpraradiary layer and have intimate connections with 

 the zonal layer. (Text-figure 17.) 



There is not a dense interradiary plexus and the fibres of the association system are few 

 in number, medium in size, and confined to the depths touching the white substance. 



FIG. 17. Radiary zone in lobus pyriformis. x-f*. 

 Note the absence of fibres of large calibre and the straggled arrangement of the radiations of Meynert. 



Type of Cell Lamination. (Plate XVII, fig. 2.) 



The plexiform layer is of unusually great depth, and a remarkable arrangement is found 

 at the point where it should give way to the layer of small pyramidal cells. Practically 

 none of the last-mentioned elements can be identified, their place being taken by curious 

 cell nests or groups, which give a bizarre appearance to the cortex and require careful 

 description. Two different varieties of nests exist : the more prominent are made up of large 

 elements, called by S. Ramrfn y Cajal polymorphous giant cells, and alternate with the lesser 

 groups, made up of small cells pyramidal in form. Taking the large polymorphous cells first, 

 it is found that they have an average diameter of 28 fj, ; they favour a stellate form, and show 

 four or five thick processes issuing in all directions. The nucleus is small and located near 

 the centre of the body. Any chromophilic elements which they may possess are of small 

 size, and do not give depth of colour to the body in Nissl preparations. The cells forming the 



