186 Cortical Structure of the Gi/rus Fornicatm [CHAP. 



TYPE OF CELL LAMINATION. (Plate XIX, tig. 2.) 



The type of cell lamination is more peculiar than the fibre-arrangement and a good 

 many points call for special notice. Two are of particular importance : first, the elements 

 corresponding to the large pyramidal cells in other regions have, in addition to other 

 peculiarities, a remarkable affinity for the stain, and secondly there is a complete absence 

 of cells of large size. Coupled with the absence of large medullated fibres, the latter truth 

 is in agreement with what has been noted elsewhere to the effect that such fibres do not 

 exist in regions where the cells are small. 



Considering the various laminae in detail we find that, (1) the plexiform layer calls 

 for no special notice. (2) The small pyramidal cells do not form a marked lamina, that 

 is to say, not being numerous they do not present the aggregated appearance seen in other 

 regions ; this specially refers to the part of the gyrus next the corpus callosum. (3) The 

 layer of medium-sized pyramidal cells is hard to define, in fact the best way to describe 

 this and the succeeding layer is to say that the usual place of the medium-sized and large 

 pyramidal cells is occupied by a single deep lamina composed of cells of approximately equal 

 size but slightly larger in the lower parts. These cells vary in measurement between 15 by 

 30 and 20 by 37 p., they have the form of an equilateral triangle, with one fairly stout 

 apical and two or three delicate basal processes, and it is important to notice that the 

 general arrangement is disorderly, and that the apical process as often as not points obliquely 

 instead of directly towards the surface : in this way they differ markedly from pyramidal 

 cells in most other parts. Then again, although the individual chromophilic elements in 

 the bodies of these cells are very difficult to define, the plasma possesses some property 

 which causes it to retain the stain firmly and hence they stand out with unusual boldness. 

 As the drawings show, the number of these cells is great. (4) In addition to the curious 

 cells just described, an even more important feature to be taken as characteristic of this 

 cortex is that the layer of stellate cells, a most constant constituent of other fields, here 

 defies definition. Only in the more peripheral parts of the area are a few small cells seen 

 in this position, gradually increasing in number as the investing convolutions are approached. 

 (5) There is also no internal layer of larger pyramidal cells. (6) The arrangement of cells 

 in the deeper parts is not alike all over the field, for a certain special feature exists by 

 which the area can be subdivided into an anterior and a posterior portion. 



In the anterior portion lie specific chromophilous cells. They occupy the upper part 

 of the fusiform layer, and although at first glance they might be taken for fusiform 

 cells, closer inspection will show that their real shape is comparable with that of an elongated 

 pyramid or pear : especially is the,, length of the apical process out of all proportion to the 

 size of the cell-body, and from the base two or three slender processes extend. The general 

 shape and the relative size of these cells are illustrated in text-figure 19, and it may be 

 therein further noted that they are considerably larger than the fusiform cells, which we 

 are familiar with in other parts, and of which we see typical examples lower down in this 

 very cortex. But not only is the shape of these cells peculiar, they have an affinity for 

 the dye which is greater than that exhibited by any other cells in the entire cerebral 

 cortex, and much greater than that of the overlying pyramidal cells, which, as I have 

 already stated, also possess this peculiarity ; on this account they stand out with remarkable 

 prominence, and their processes even in Nissl specimens are traceable for a great distance. 



