_Dilatation of the Pupils_.--Gratiolet repeatedly insists[24]
that the pupils are enormously dilated whenever terror is felt.
I have no reason to doubt the accuracy of this statement,
but have failed to obtain confirmatory evidence, excepting in the one
instance before given of an insane woman suffering from great fear.
When writers of fiction speak of the eyes being widely dilated,
I presume that they refer to the eyelids. Munro's statement,"
that with parrots the iris is affected by the passions,
independently of the amount of light, seems to bear on this question;
but Professor Donders informs me, that he has often seen movements
in the pupils of these birds which he thinks may be related to their
power of accommodation to distance, in nearly the same manner
as our own pupils contract when our eyes converge for near vision.
Gratiolet remarks that the dilated pupils appear as if they were
gazing into profound darkness. No doubt the fears of man have often
been excited in the dark; but hardly so often or so exclusively,
as to account for a fixed and associated habit having thus arisen.
It seems more probable, assuming that Gratiolet's statement
is correct, that the brain is directly affected by the powerful
emotion of fear and reacts on the pupils; but Professor Donders
informs me that this is an extremely complicated subject.
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