18 Histology of the Island of Red. By Herbert C. Major, M.D. 
Now the first point I desire to establish is this — that the plan 
of arrangement of the cortical layers in the Island of Red differs 
in no respect from that I have already alluded to as being the 
ordinary one throughout the cortex. If the layers delineated in 
Plate CLXXXY. be compared with those figured by Meynert, it 
will be seen that, with exception of that which I term the fifth 
layer, and which Meynert does not notice as distinct from the 
deepest, the resemblance is nearly complete. The cells may not 
have the same relative or absolute size — that is a point which will 
be considered shortly — hut their general aspect as seen with a low 
power of the microscope, and their relative numbers in the several 
layers, correspond very closely. 
With regard to the intimate constitution and appearance which 
the nerve-cells of the Insula present, as seen under a power of 350 
diameters, I can observe nothing unusual, — nothing that would 
seem to imply (as in the case of the so-called giant-cells of the 
vertex) any special and peculiar functions. Even with the highest 
magnifying power at my command ( one-tenth objective, Hartnack), 
I can detect no departure from those characters which are so well 
recognized. 
The size of the nerve-cells of the Insula, as of all other parts of 
the cerebrum, deserves special attention. I gather from the 
account of Dr. Lockhart Clarke,* that, while he considers the 
nerve-cells of the Insula to be generally larger than in some other 
parts, yet that they are not as large as those commonly found in 
the convolutions of the vertex. f I am quite sure of the general 
accuracy of the above remark, but would wish to extend the 
observation and render it more precise by an appeal to actual 
measurement of the cells of the various layers as taken with the 
micrometer. 
1st layer. The small and for the most part nucleus-like bodies 
which occur in this layer, I find measure '008 millimeter, the 
occasional nucleated corpuscles being about "012 millimeter 
(Plates CLXXXY., CLXXXVI., 1 P). 
2nd layer. The small pyramidal bodies of the second layer 
(CLXXXY., CLXXXVI., 2 2'), average ‘012 millimeter, occa- 
sionally reaching ’016 millimeter. 
3rd layer. The cells of the third layer vary between - 016 at 
the superficial portion of the stratum, to • 024 or even * 028 
millimeter (occasionally only) at the deepest part. It will be 
observed that in this layer, as the cells increase in size, they 
diminish in number (CLXXXY., CLXXXVI., 3 3'). 
4th layer. The small oval or pyriform bodies of this layer, 
which impart to the stratum so distinctive an appearance, owing to 
* Maudsley’s 1 Physiology and Pathology of Mind,’ 3rd ed. p. 115. 
+ This is, I believe, Dr. Clarke’s meaning. 
