56 HIS, ON THE CORNEA. 
undergo no corresponding enlargement. This fact is worthy of particular 
attention, because, as we shall see, it lays the foundation for subsequent 
much more important differences. 
“The cells external to the area of irritation appear dilated in the superficial 
layers, but as yet without division of the nuclei and retraction of the 
contents ; in the cells of the deeper layers of the whole cornea hardly any 
change is perceptible.” —pp. 79—82. 
At two or three hours the alterations are of the same nature, 
though they have extended further both in the thickness and 
over the surface of, the cornea. At from sixteen to twenty 
hours the retraction of the cell-contents from the cell-wall 
has extended even to those corneal cells which lie close to the 
membrane of Descemet, and the same changes gradually 
take place in the deeper, as have already been described in 
the more superficial layers. Segmentation of the contents 
has but rarely taken place in the deep layers, but increases 
in frequency towards the surface throughout the whole 
cornea. 
“A complete series of stages of development is observable if we pass 
from the deep to the superficial layers. Solitary cells are seen with a single 
large granular content-mass ; in others, the contents have divided into two 
or more segments; among these are some which, together with the content- 
masses, contain one or two endogenous cells, and lastly, at the surface (in 
the peripheral part of the area of irritation), the corneal cells are changed 
into large and wide anastomosing sacs which are completely filled with a 
brood of endogenous cells, and in which no granular content-masses can any 
longer be seen. In some of these saccular corneal cells there are not more 
than two or three endogenous cells, but others contain twenty and more, 
and are many times larger than their normal size. The fundamental form 
of all the endogenous cells is round; but when aggregated in great numbers 
they frequently become polyhedral, by mutual flattening.”—p. 85. 
Dr. His remarks that in this stage the area of irritation, 
when examined with the naked eye, presents centrally and 
peripherally a turbid appearance, while the imtermediate 
portion is clearer. Now, in this intermediate space the cells 
exhibit hardly any endogenous cells, but only, as it were, 
the early changes leading to their formation. The central 
part, on the contrary, is as greatly altered as the peripheral, 
but from a different cause, namely, from the presence of 
innumerable nuclei, which have become developed by the 
subdivision of the nuclei of the corneal cells, and are now 
arranged in lines corresponding with the processes of the 
cells. The bodies of the cells, instead of bemg distended, as 
at the periphery, have commonly ceased to be distinguishable. 
Dr. His doubts whether these nuclei are surrounded by dis- 
tinct cell-walls. 
After sia days, the cornea is clouded throughout, and 
in the centre it appears yellowish and opaque, while parallel 
close-set vessels radiate from the margin over a zone of half 
