254 The Island of Reil [CHAP. 



Layer of Medium-sized Pyramidal Cells. 



All that I would say about this layer is that it is not up to the average in depth 

 and that it fades insensibly into the subjacent layer. 



External Layer of Large Pyramidal Cells. 



We now reach a layer of greater interest. The constituent cells being very numerous 

 and staining sharply form a quite prominent lamina. They differ from corresponding cells 

 in other cortical regions (e.g. the parietal, temporal, and frontal cortex) in point of size 

 and configuration ; thus, they are small, lacking in plumpness, tapering and much elongated, 

 the apical process being drawn out; also the base of the cell is angular instead of rotund 

 and from these angles issue three, four, or even five delicate processes ; the body substance 

 stains freely and more or less uniformly ; the nucleus inclines to be oval in shape and 

 small, and the nucleolus is distinct. 



Descending towards the limen insulae the same cells suffer a reduction in size and 

 number. 



In the gyrus brevis primus one occasionally sees in the midst of the layer, looking 

 very much out of place, a larger and plumper cell endowed with distinct chromophilic 

 particles, and I see no other way of explaining these than by regarding them as dislocated 

 members of the orbital extension of the " intermediate precentral " area. 



When the posterior insular type is described differences affecting this lamina will be 

 indicated. 



V 



Layer of Stellate Cells. 



It is a point of some importance that this layer is very indifferently represented, indeed 

 it is hardly recognisable as a lamina, a break in the lamination and the presence of a few 

 typical triangular and polymorphous elements only just mark its position. 



Internal Layer of Large Pyramidal Cells. 



Here follows another prominent lamina not so deep as the corresponding external layer, 

 but chiefly made up of cells similar in size, shape, and staining properties. In addition, 

 however, and particularly towards the limen one finds very remarkable cells calling "for 

 special notice. These are large bipolar cells of spindle form and great length, elements 

 which stain very intensely in this way reminding one of cells seen in the great limbic 

 lobe and which are entirely different in shape, size, and staining reaction from the cell 

 with which we are familiar as the common constituent of the fusiform layer. , Occa- 

 sionally the two poles of the cell are of equal length and the nucleus is centrally situated, 

 but more often the lower part is only a fraction of the size of the upper and the nucleus 

 is dropped accordingly. Attention is drawn to these cells in the text-figure 23, and I will 

 end my description of them by saying that the most typical examples are met with in 

 the gyri breves and that they seem to attain their best development along the crown of 

 these gyri ; as we proceed downwards over the " pole " of the insula, although they lose 

 in size, they gain in number; and they are particularly numerous in that part where we 

 saw an exaggerated zonal layer, hence the impression is given that they are aberrant elements 

 of the limbic cortex, which have spread up from the inferior surface. 



