52 
MR. W. BEVAN LEWIS ON THE COMPARATIVE 
measuring 5/x, with a large spheroidal nucleus, and a true connective corpuscle, 
averaging 9/x in diameter, having one or more nuclei, and when not altered by 
reagents seen as a corpuscle of irregular contour with numerous delicate radiating 
processes. As I have stated elsewhere,I regard the latter as the origin of 
Deiter’s corpuscle, to which frequent allusion has been made. The coarser connec¬ 
tive element recognised as Deiter’s cell is present immediately beneath the pia mater, 
but far less abundantly than in the Pig and Sheep. The nuclei of these cells usually 
measure 4/x in diameter, whilst the nucleus of the angular cell, which in general 
conformation sometimes approaches them, measures fully 9/x. The superficial portion 
of this layer presents us with the usual belt of medullated fibres extending to a 
depth of ‘162 mm. to T92 mm., the individual fibres of which measure 2/x to 4/x in 
diameter. 
Second layer. —Tins stratum, far better marked than in the Sheep, is constituted 
of small angular, ovoid, or pyramidal cells. The angular cell is frequently bifurcate 
or horned, and branches irregularly. All the cells contain a large oval or spheroidal 
nucleus, and are imbedded in a matrix identical with that of the first layer. Here 
we also recognise the large connective cell. The nerve-cells of this layer average 
10/xX 6/x, with a nucleus 5/x in diameter; but amongst them are found larger pyramidal 
cells, identical in appearance with those of the upper part of the third layer, and which 
attain the dimensions of 13/xX 10/x. The depth of this layer varies between , 139 mm. 
and T86 nun. 
Third layer. —Tins layer and the one superimposed appears to the naked eye as 
a dark grey translucent band, and extends to the depths of 744 mm. to 790 mm. 
The pyramidal elements characteristic of this formation increase in size with their 
depth, as do the corresponding cells in the cortex of Man and Apes. The average 
dimensions of these cells is 16/xX9/x, the larger cells at the lowest levels of this 
stratum attaining proportions of 23/xX 13/x. Seven processes are usually seen in ver¬ 
tical sections. In the immediate neighbourhood of the crucial sulcus the largest cells 
of this layer do not extend below the upper half of the stratum, leaving betwixt 
them and the ganglionic series a paler band, in which are very sparsely scattered a 
few smaller pyramidal cells and angular elements, the latter being found at all depths 
of this layer, although in very small numbers. On the parietal side of the sulcus, 
however, the pale band becomes a belt of small angular elements. Thus, although 
the angular cells are found at all depths from the second layer downwards, they do 
not constitute a distinct stratum betwixt the large pyramidal and ganglionic layers 
until the parietal boundary of the crucial sulcus is reached, and the limits of the anterior 
portion of the limbic arc overstepped. Perivascular and connective cells of the same 
character as those of superimposed layers appear here. The matrix consists of an 
extremely delicate connective with a meshwork of the minutest nerve-fibrils given off 
from the angular elements and the periphery of the small and large pyramidal and 
'* Loc . cit . 
