v] VisMO-S&n&ory Ti/pe of Cell Lumint!<i 115 



TYPE OF ARRANGEMENT OF NERVE CELLS. (Plato XI, tig. 1.) 



Just as the arrangement of nerve fibres in this area is absolutely distinctive, so also 

 it is characterised by quite a special type of nerve cell lamination, indeed it is as easy 

 t" map out the area, in serial sections stained according to the method of Nissl, as it is 

 in those stained for the display of nerve fibres. 



But since this type of cell lamination has been examined with extreme thoroughness 

 by other observers (notably Ramon y Cajal and Bolton) the following remarks must neces- 

 sarily be of a recapitulatory nature; they will also be framed to emphasise the features which 

 interest the topographist rather than the minute histologist. 



That there may be no confusion concerning the different laminae to which I shall 

 allude, I would at once mention that I am following the classification adopted by Ramdn 

 y Cajal ; and I would refer those who desire details on the relation of this classification 

 to others published, to Bolton's paper, where the arrangements adopted by himself are 

 compared in tabular form with those of Meynert, Krause, Betz, Leonova, Hammarberg, 

 Schlapp, and Ramon y Cajal. 



Plexiform Layer. 



While affording no indication that special elements reside in this layer, Nissl specimens 

 clearly show that its total depth is less than in other cortical regions, a fact which did 

 not escape the notice of Meynert, and which, as Ram6n y Cajal points out, is probably 

 due to the relatively small number of medium-sized and large pyramidal cells present in 

 subjacent parts. 



From an examination of his chrome-silver preparations Ramc'in y Cajal draws attention 

 to the existence of certain special, horizontally-directed cells in this layer, cells which he 

 thinks act as a medium in bringing the large association fibres of this layer into dynamic 

 relation with the pyramidal cells of neighbouring convolutions. 



Layer of Small Pyramidal Cells. 



From the topographic point of view the only feature of interest presented by this 

 layer is the close manner in which its constituent cells are arranged. 



Layer of Medium-sized Pyramidal Cells. 



The shape of these cells is similar to that of the cells immediately above, but their 

 size is greater and they stand further apart from one another. It is also to be noticed that 

 in the lower part of the layer small stellate cells are dotted about, and that larger pyramidal 

 cells, in which distinct chromophilic particles may be seen in the protoplasm of the cell-body, 

 are occasionally present. 



Layer of Large Stellate Cells. 



The nature and arrangement of the cell elements in this lamina are so distinctive that 

 they must be described at length. 



152 



