116 Visuo-Sensory and Visuo-Psychic Areas [CHAP. 



The layer is a broad one, measuring about '3 mm., and the large pyramidal cells which 

 occupy a homologous position in other cortical territories are almost entirely absent; their 

 place being taken by curious large stellate cells, intermingled with which are smaller bodies 

 resembling those seen in the subjacent stellate layer proper. 



Concerning the larger variety of stellate cells, they lie chiefly in- the outer zone of 

 the lamina, and are of curious, triangular, or quadrilateral form ; they have three or four 

 stout processes pointing in no definite direction, and they contain scattered clumps of 

 chromophilic material. They are not of great size, only measuring about 25 /i in diameter, 

 nor are they specially numerous, hence they do not form a prominent lamina when viewed 

 under a low power of the microscope, and as a matter of fact the whole layer has a 

 pallid appearance in comparison with the layer of medium-sized pyramidal cells above and 

 the dense stellate layer below. In seeking an explanation of this pallid appearance we have 

 merely to turn to our specimens stained for nerve fibres, wherein we shall find that a 

 large part of the corresponding zone is occupied by the dense plexus of fibres which we 

 described under the name of the line of Gennari. Moreover, we have Ramon y Cajal's 

 evidence that in Golgi preparations the above-mentioned large stellate cells and a variety 

 of the same cells which he finds at this level, have strong, horizontally directed dendrites 

 which branch frequently and extend long distances, also axis-cylinder processes which send 

 out stout collaterals to ramify in the vicinity of the cell itself and in the immediately 

 subjacent stellate layer, and clearly these add to the density of the fibre plexus in the 

 line of Gennari and help to increase the pallor of the field in Nissl preparations. 



Layer of Small Stellate Cells. 



Bounded above, and, as we shall presently see, below also, by a pallid zone, the stellate 

 layer, which is about "17 mm. deep and heavily stocked with cell elements, forms a pro- 

 minent lamina. 



In Nissl specimens the component cells appear as minute angular bodies with a rela- 

 tively large nucleus, and they are separated into vertical columns by the fasciculi of radiating 

 fibres which pierce the layer. 



It seems that in Golgi preparations several varieties of stellate cells 111:13- be proved 

 to exist, but for details concerning these the reader is referred to Ramdn y Cajal's work. 



Layer of Small Pyramidal Cells with, an Ascending Axis-Cylinder. 



Rami'm y Cajal is responsible for the differentiation of this layer of small pyramidal 

 cells, for which he finds a place immediately below the stellate layer, and about which he says, 

 that as the morphology of the cells is so peculiar (the method of Golgi shows that they 

 have an ascending axis-cylinder process and that they may be egg-shaped, stellate or strictly 

 pyramidal in form) their recognition as a separate layer is warranted. But in point of 

 fact it can hardly be said that they form a distinct lamina, because they are sparsely 

 scattered over an otherwise pallid area, at the bottom of which lie the great pyramidal 

 cells or solitary cells of Meynert, and in Nissl specimens they exhibit no features of special 

 interest. 



