Histology of the Island of Beil. By Herbert C. Major, M.D. 19 
tlieir small size and especially to their great uniformity, measure, 
with few exceptions, ' 012 millimeter. Occasionally, as in other 
parts, a large cell measuring • 02 or even • 024 millimeter is seen, 
but this is rare. The sudden diminution in the size of these bodies 
as compared with those of the previous layers is very striking, 
coinciding, as the fact does, with the result of simple observation. 
5th layer. In this layer, I believe, more than in any other, the 
cells vary in size, and it is the more difficult to give an approximate 
average. I think, however, that the dimensions '02 to - 224 
millimeter will include most of the corpuscles. Many, however, are 
very much smaller, while, on the other hand, some occasionally occur 
measuring • 032 millimeter in length (CLXXXV., CLXXXVI., 5 5'). 
6th layer. The corpuscles of this, the deepest cortical layer, are 
for the most part spindle-shaped, more especially in that part of the 
cortex forming the summit of a gyrus, and hence their length is very 
disproportionate to their breadth. Average length, ’02 to • 024 
millimeter; breadth, • 008 millimeter (CLXXXV., CLXXXV L, 6 6'). 
The above results are those afforded by the healthy brain to 
which I have before alluded, but they have been supplemented and 
confirmed by measurements taken in twelve other cases, which, 
although morbid, afford valuable confirmatory evidence. It is 
hardly necessary to point out the impossibility of giving in any 
instance the exact dimensions of all the corpuscles, a fair average 
derived from a large number of observations being the most that 
can be afforded. 
Taking now a section from a convolution of the vertex ( frontal 
region), it will be seen that the estimated dimensions of the cells 
show a close resemblance as regards absolute as well as relative size, 
thus (as before, in fractions of a millimeter) : 
]st layer - 00S to "012 mil iineter. 
2nd layer ’012 „ *02 (rarely) millimeter. 
3rd layer -02 „ -028 ' „ 
4tli layer ’012 „ '02 (rarely) „ 
5th layer '02 „ ’024 „ 
Gth layer '016 „ ’02 „ 
Now a comparison of the above figures with those before given 
as representing the size of the cells in the Insula, might hardly 
seem to warrant the statement formerly put forward that in the 
latter situation the cells are smaller than at the vertex. The truth, 
however, and its explanation, appear to be this : The third layer 
is that in which the contrast occurs. In the Insula cells are found 
quite equal in size to those in the corresponding layer at the vertex 
(I exclude, of course, from consideration the so-called giant-cells ) ; 
but the majority are smaller; and hence it is that while in a 
section taken from the vertex the band of cells forming the third 
