quite fanciful, but
as you say that the eyeball advances in adaptation for vision for close
objects, would the eyeball have to be pushed backwards in adaptation for
distant objects? (470/4. Darwin seems to have misunderstood a remark of
Donders.) If so, can the wrinkling of the lower eyelids, which has often
perplexed me, act in pushing back the eyeball?

But, as I have said, I daresay this is quite fanciful. Gratiolet says
that the pupil contracts in rage, and dilates enormously in terror.
(470/5. See "Expression of the Emotions," Edition II., page 321.) I have
not found this great anatomist quite trustworthy on such points, and am
making enquiries on this subject. But I am inclined to believe him, as
the old Scotch anatomist Munro says, that the iris of parrots contracts
and dilates under passions, independently of the amount of light. Can
you give any explanation of this statement? When the heart beats hard
and quick, and the head becomes somewhat congested with blood in any
illness, does the pupil contract? Does the pupil dilate in incipient
faintness, or in utter prostration, as when after a severe race a man
is pallid, bathed in perspiration, with all his muscles quivering? Or in
extreme prostration from any illness?

LETTER 471. TO W. TURNER. Down, March 28th [1871].

I am much obliged for your kind note, and especially for your offer of
sending me some time corrections, for which I shall be truly grateful. I
know that there are many blunders to which I am very liable. There is
a terrible one confusing the supra-condyloid foramen with another one.
(471/1. In the first edition of the "Descent of Man," I., page 28,
in quoting Mr. Busk "On the Caves of Gibraltar," Mr. Darwin confuses
together the inter-condyloid foramen in the humerus with the
supra-condyloid foramen. His attention was called to the mistake by
Sir William Turner, to whom he had been previously indebted for other
information on the anatomy of man. The error is one, as Sir William
Turner points out in a letter, "which might easily arise where the
writer is not minutely acquainted with human anatomy." In speaking of
his correspondence with Darwin, Sir William remarks on a characteristic
of Darwin's method of asking for information, namely, his care in
avoiding leading questions.) This, however, I have corrected in all the
copies struck off after the first lot of 2500. I daresay there will be
a new edition in the course of nine months or a year, and