HIS, ON THE CORNEA. ao 
they elongate and become dumb-bell or drumstick-shaped. Many of them 
are divided into two segments of altogether different form and size, and this 
change is found most frequently, on the one hand, in the immediate neigh- 
bourhood of the point of irritation, and on the other in the peripheral por- 
tion of the area of irritation. The superficial cells which lie external to 
the area of irritation, are far less affected than those just described; they 
are, indeed, as a general rule, more clearly visible than in the normal state, 
whence we may conclude to a widening of their cavity; but in other 
respects they exhibit no remarkable peculiarities. In like manner those 
corneal cells which are not close to the surface exhibit no perceptible 
change ; their bodies are not enlarged, and their nuclei are neither shrunken 
nor notched. 
“One hour after irritation the rabbit’s cornea exhibits an essential ad- 
vance. The dilatation of the cells, the peculiar alteration in shape, and 
partial division of the nuclei, has extended from the surface inwards; here 
also the cell-contents appear remarkably coarsely granular, and begin in a 
singular manner to retract from the cell-membrane. In fact, in the superficial 
layers, the contents have aggregated more closely around the nucleus, so as 
often completely to obscure the latter, and at the same time to leave a clear 
space between themselves and the dilated cell-membrane. The contents in 
this way form a kind of independent mass, everywhere separated from the 
cell-wall, and though repeating the form of the cell-cavity, surrounded by no 
membrane, but consisting of a mere granular conglomerate. In many of these 
masses of contents, the outlines of the nucleus are still distinguishable; but 
in others the nucleus is completely obscured, and in these cases one may 
easily be led to suppose that the contents and nucleus are the nucleus alone ; 
and this is the more easy, since after a time the nucleus in the interior, 
appears to swell and to become enlarged out of all proportion. ... . The 
withdrawal of the cell-contents from the wall is most remarkable at the 
edge of the cornea, or, in other words, in the peripheral part of the area of 
irritation ; here also the corneal cells are most enlarged, and in correspond- 
ence with the frequent divisions of the nuclei already observed in this 
region, we now meet in equal abundance with segmentation of the con- 
tent-masses agglomerated round the nuclei. These masses have in many of 
the cells broken up into two or more irregular portions of usually very 
unequal size. Under favorable circumstances a nucleus is discernible in 
each portion, and occasionally two are seen in the larger masses, so that it 
seems probable that the contents have divided in those cells only in which 
the nuclei have already multiplied. 
“The content-masses often send one or more branches inio the principal 
processes of the cells; and in the divided ones, these elongated portions 
have become separated from the rest. A process which commences, even at 
this early period, in some corneal cells, is the formation of endogenous cells. 
Among the peripheral cells with divided contents, in fact, there are some 
in which, instead of one or other of the separated masses of contents, a 
small rounded cell, with a cavity distinctly bounded by a membrane and a 
rounded, somewhat dark-contoured granular nucleus, is visible. This little 
cell, like the granular mass of contents itself, is not in immediate contact 
with the membrane of the corneal cell ; but is at first separated from it by 
a more or less broad clear space. It is frequently imbedded in a regular 
pit of the mass of contents, and so obviously fills the place of a separated 
segment of contents that it can hardly be doubtful it has arisen from such 
a segment, the granular mass surrounding the nucleus having differentiated 
itself into membrane and contents. 
“The cells about the ‘point of irritation’ (in these experiments, the centre 
of the cornea), exhibit a very different relative development, inasmuch as in 
them the process of division of the nucleus predominates, while the cells 
VOL. VI. F 
