48 
MR. W. BEVAtf LEWIS ON THE COMPARATIVE 
spider-like bodies known as Deiter’s cells are met with. They are distributed espe¬ 
cially along the course of the blood-vessels which vertically traverse this superficial 
layer of the cortex. Closely packed beneath the pia mater, their long filaments 
spread in all directions embracing the nearest blood-vessel. They thin out in numbers 
below the upper third of this layer, becoming few, and scattered widely apart in the 
neighbourhood of the small pyramidal layer. It may here be stated that these peculiar 
bodies are found in very scant numbers throughout the various subjacent layers, but 
towards the lower realms of the spindle layer they again congregate in larger numbers, 
become especially abundant along the blood-vessels which course through the medullary 
strands at the confines of the cortex. It is evident from this distribution that they 
are more especially limited to the regions of the greater vascular channels, and do not 
intrude upon the regions of capillary distribution. This fact I regard as significant, 
when we also take into consideration their reappearance in Man as morbid elements 
in those diseases of the brain which are regarded as closely connected by a causal 
relationship with extensive vascular lesions. The pia mater is not only thickened, but 
is strongly attached to the cortex by means of these bodies, and over certain regions, 
as the two lower parietal convolutions, the adhesion is so strong that the pia cannot 
be separated without destroying the subjacent layer. In these regions of firm 
adhesions betwixt the pia mater and cortex the processes of these cells are extremely 
coarse, and often form a dense felt of fibres immediately beneath the pia. Such a 
condition I have not observed in Man except as the result of retrogressive changes in 
diseased regions. The depth of this characteristic formation is usually ‘134 mm., 
and varies from -g-rd to Tth the depth of the first layer. The other elements of this 
layer resemble in all essential features those of the corresponding formation in the Pig. 
Second layer (Plate 6, B).—In the five-laminated region of the limbic lobe which we 
are now considering, this formation is peculiarly poor in cells and forms but an insigni¬ 
ficant belt of small angular and pyramidal elements associated with larger pyramidal 
cells. It is often apparently absent, or forms by the closer approximation of its 
elements a limiting border to the important layer below it. This layer becomes deeper 
and more decided towards the posterior pole of the hemisphere. Again, in the anterior 
extremities of the lower parietal convolutions it is a more distinct formation. The 
cells are oval, angular, or small pyramids possessing a large spheroidal nucleus. The 
smaller cells average 13p-X6/x in dimensions, their nucleus having a diameter of 6/n 
Th ird layer (Plate 6, C).—The cells of this layer are remarkably uniform in size 
throughout, and in the anterior portion of the superior arc of the limbic lobe they are 
most densely aggregated in the upper half of the layer, their comparative paucity in 
its lower half gives to this region the appearance of a pale white belt. The whole 
layer is of fair depth, and presents but few of Deiter’s corpuscles above alluded to. 
The cells vary much in contour, although the majority are pyramidal in form, their 
nucleus measures 6/x in diameter, and the cells average 18/x X 10/x. Their apical 
process is frequently contorted and twisted in its course upwards towards the first 
