Sir/

Upon reading your recent Book upon Expressions, I am led to write to you on two subjects of which you treat.

I make my apology for addressing you, as we are strangers, and trust my good will may be my excuse.

With regard to the gestures of the body in surprise, the raising of the open hands.²

I suggest that when you are surprised at a thing, you throw your body back from it, so that your body is off its balance.

When you step on a piece of orange peel in the street, and your foot slips forward so as to throw your body off its balance backward, you throw your arms violently up, with the fingers open, and so recover your balance, and walk on.

So, when your body is off its balance from being thrown back from the object surprising you, you recover your balance by throwing up your hands with the fingers widely stretched, because you obtain the resistance of the air better so, and so recover your balance.

When education has given you self command, surprise does not cause you to start back, or to raise your hands, but the power of association remains, and when you unbend, such as to listen to a child telling you some simple piece of wonderfulness, you naturally raise your hands to express, to please the child, surprise you do not feel.

As to the heart beating quickly and violently, and the exudation of perspiration from a cold skin, in fear.

It might be suggested that, when you were part of your ancestors, you ran from what you were afraid of, and the exertion made your heart to beat, and your perspiration to run, and now, although you may not run from what you may fear, from an educated self command or other means, the power of association makes the heart beat quickly and violently, and the perspiration exude.³

The last four pages of your chapter on weeping might be applied, I venture to suggest, to the sudorific as well as the lachrymal glands, and it would appear natural that the involuntary habits of the body should be very tenacious, because they can not be overlaid by personal peculiarities and affectations.⁴

Again apologising for troubling you with what is loosely expressed, and has probably been already fully considered by you, I remain | Sir | Your obedient servant | H Henry

Chs Darwin Esq^re. M A. FRS | Royal Society