58 HIS, ON THE CORNEA. 
influence ; while, on the other hand, the increase’ of the cell in size is in relation 
with the amount of matter supplied by the neighbouring vessels. 
“‘ We should express this at once as a law, that the vessels take no direct 
share in the origination of inflammatory histological changes, if observation 
did not furnish us with a fact in apparent contradiction therewith. If the 
influence of the irritant and that of the vessels could be regarded simply as 
two forces operating from two points on an intermediate space, with an 
intensity inversely proportional to the distance from their centres, then if the 
division of the nuclei were regarded as the effect of the stimulus—the in- 
crease of the cells as that of the vascular influence—the locality of the 
least nuclear division ought to coincide with that of the greatest cell- 
growth, and vice versé. Now observation shows that the latter is the ease, 
but not the former; for the point of least nuclear division falls, as we have 
seen, not at the margin of the cornea, but in the zone between it and the 
centre, the increase in the number of nuclei at the margin being from the 
very beginning by no means small. 
“Two possibilities offer themselves when we seek for an explanation of 
this fact; either the irritation proceeding from the centre undergoes a local 
intensification, in which case some nervous influence would suggest itself ; 
or we may assume that the peripheral cells, from the more favorable con- 
ditions of their existence, (the more ready supply of nutriment,) possess a 
greater irritability than the cells of the centre of the cornea, whence, with a 
slight irritation they react more intensely than the latter with a stronger 
irritation. 
“The last view appears to be the more unconstrained and natural—and 
we must especially completely renounce the idea of any direct influence of 
the nerves on the processes of nuclear division, since in the deep nerveless 
layers of the cornea the growth of the nuclei goes on in the same way as in 
the superficial ones, as soon as the irritant comes to act directly upon these 
more deeply seated parts.”—p. 113. 
Objections might be raised to the demonstrative force of 
the evidence on which Dr. His bases these conclusions. It is 
unfortunate that we do not know the effect of varying the posi- 
tion of the point of irritation, which would probably be very 
instructive. And it must be remarked that the direct in- 
fluence of a stimulant upon the life of the cell, or, in other 
words, in producing dilatation and nuclear division, is not 
proven; for one immediate effect of the stimulant is to alter 
through the nerves the state of the cireumcorneal vessels, and 
it is impossible to say, from Dr. His’s experiments, whether 
the earliest changes observed are the direct effect of the 
stimulant, or the indirect consequence of the modification 
produced by that stimulant on the supply of nutriment. 
Dr. His details certain observations upon the changes of 
texture exhibited by the cornea after section of the fifth nerve 
and in carcinoma melanodes ; and he concludes with some re- 
marks upon the histology of arcus senilis, whose true nature 
and connection with other forms of fatty degeneration were 
first shown by Mr. E. Canton. But into these matters we 
do not propose to enter, and we have only to add that Dr. 
His’s work is illustrated with numerous and excellent figures. 
