j4 Ilia ology of the Island of Beil. By Herbert C. Major, M.D. 
confine myself to the two extreme genera in each tribe, and one or 
two intermediate ones. It will be easy for observers familiar with 
the study of diatoms to intercalate those genera he wishes to 
classify, by taking notice of the modifications of the endochrome 
which cause the difference of genera.” 
(To be continued.') 
IY. — The Histology of the Island of Beil. By Hebbert C. 
Major, M.D., Medical Director West Biding Asylum. 
Plates CLXXXY. and CLXXXVI. 
The present article is intended to form the first of a series having 
for its object the investigation of the minute structure of the Island 
of Beil as found in the human brain under varying conditions and 
in the ape. 
Little need here be said with the view of advocating the claims 
of the Island of Beil, Insula, or Central lobe of the brain, as being 
worthy of the closest and most careful study on the part of the 
anatomist ; not that it is more important than any other part of 
the cerebrum, but because, in some respects, it has special features 
of interest. It is that part of the brain which appears earliest both 
in the human foetus and in the animal series. It appears to be 
peculiar to man and the higher apes ; with the exception of the 
Makis, no indication of its presence being observed in other animals.* 
Situate also as the lobe is, deeply in the cerebral mass, and con- 
cealed between the frontal, parietal, and temporo-sphenoidal lobes, 
it is, in those of the lower animals in which it occurs, peculiarly 
difficult of access to the experimental investigator. And finally, 
there would seem to be good grounds for believing that this region 
of the cortex is connected in an especial manner with the exercise 
of the faculty of language. 
The above facts have for the most part long been known ; but 
EXPLANATION OF PLATES CLXXXY. AND CLXXXVI. 
Plate CLXXXV. — Section through a gyrus of the Island of Eeil, showing 
the cortex of the summit of the gyrus (healthy). 
Plate CLXXXVI. — Section through the cortex of the Island of Keil at the 
bottom of a sulcus (morbid). 
In both : — I, 2, 3, 4, 5, 6, indicate the cortical layers magnified 50 diameters. 
m m, Medulla. 1', 2', 3', 4', 5', 6', cells of the various layers magnified 350 dia- 
meters. m' rn\ Medulla. In the medulla the corpuscles of Deiter (cellules 
arai^ne'es, Gratiolet) are seen. 
* Gratiolet et Leuret, ‘ Anat. Comp, du Syst. Nerveux,’ p. ill. 
