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Darwin Correspondence Project

From S. W. Pennypacker   14 September 1874

209 S 6th St | Phila. Penna

Sep 14’. 1874

Dear Sir

There are two or three physical peculiarities, exemplified in my own person, which I do not remember that you have alluded to in any of your works and which seem to be some slight additional evidence of the correctness of your scientific theories— I have entire control over the muscles which move the nostrils being able to dilate and contract them at will as rapidly and in precisely the same manner as you have doubtless often seen rabbits do when they are sitting at rest— I have known one or two other persons who possessed the same power but I think you will find upon investigation that they are extremely rare— To an animal depending for safety or subsistence upon its keenness of scent doubtless the control of these muscles would be of considerable importance but I cannot see that they are of any service to man.1 However the direction in which the fact points will of course occur to you much more readily than to me— I am also able at will to spread out the toes of both feet separating the little toe a considerable distance from the others— There has been little if any effort upon my part to acquire by exercise the use of these muscles and it never occurred to me that there was anything extraordinary in the movement of the little toe until I accidentally discovered that most persons were powerless in this respect. It seemed to me to be my duty to send you these facts—

As to whether they are of any importance or not you can of course best judge

Very Respy | Sam W Pennypacker

Charles Darwin AM

CD annotations

1.1 There … theories— 1.4] crossed pencil
1.4 I] after opening square bracket pencil


CD had described the contraction and dilation of the nostrils in animals and humans in Expression, pp. 130–1, 143, 152, 240, 256, and 308.


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


He has physical peculiarities that support CD’s theories: e.g., ability to dilate nostrils like a rabbit and to spread out the toes of both feet.

Letter details

Letter no.
Samuel Whitaker Pennypacker
Charles Robert Darwin
Sent from
Source of text
DAR 174: 35
Physical description
3pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9636,” accessed on 19 September 2021,

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