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Darwin Correspondence Project

From W. G. Walker   6 December 1874

66, Blenheim Crescent, | Kensington Park,

6 Decr. 1874.

Dear Sir,

Last year I took the liberty on addressing you on a point that occurred to me in connection with your “Expression of the Emotions”.1 I have just finished reading the work a second time, & venture again to write to you. At the same time, please state unreservedly whether communications (of which you doubtless receive a great many) from outsiders are a nuisance to you.

You say (p. 259) “the suspicion arises that our progenitors must formerly have had the power (like that possessed by ruminants & some other animals) of voluntarily rejecting food which disagreed with them or which they thought would disagree with them”. The explanation is certainly plausible, & perhaps probable, but the conduct of the dog seems to me to present a difficulty. I suppose it is a well-known fact (I have myself observed it several times) that dogs vomit when in a perfect state of health. If this were all, it might well be supposed that they vomited intentionally, to relieve their stomachs of what is, or what they suppose to be, an unwholesome load. But when they have rejected food in this manner, they shortly afterwards proceed to devour what they have so rejected,—‘returning like a dog to his vomit’. If the food is, or is supposed to be, injurious,—whether the vomiting be voluntary or involuntary,—what can be their motive for taking it again into their stomachs?2

Trusting I shall not be thought impertinent for proposing this point, | I remain, | Faithfully yours, | W. Gregory Walker.

Ch. Darwin, Esqr.

CD annotations

Top of letter: ‘Expression | Vomiting’ ink


No reply to this letter has been found, but a note added to the cited passage in the second edition of Expression remarked that bitches often vomited up food for their young when the young had reached a certain age (Expression 2d ed., p. 271 n. 11).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Expression 2d ed.: The expression of the emotions in man and animals. By Charles Darwin. 2d edition. Edited by Francis Darwin. London: John Murray. 1890.

Expression: The expression of the emotions in man and animals. By Charles Darwin. London: John Murray. 1872.


On voluntary vomiting. Dogs re-swallow vomited food.

Letter details

Letter no.
William Gregory Walker
Charles Robert Darwin
Sent from
London, Blenheim Crescent, 66
Source of text
DAR 181: 5
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9745,” accessed on 26 September 2021,

Also published in The Correspondence of Charles Darwin, vol. 22