To Hubert Airy   5 April [1871]¹

Dear Sir

I am greatly obliged for your letter— Your idea about the easy turning of the head instead of the ears themselves strikes me as very good & quite new to me; and I will keep it in mind, but I fear that there are some cases opposed to the notion.²

If I remember right the Hedgehog has very human ears, but birds support your view, though lizards opposed to it—

Several persons have pointed out my error about the Platysma—³ Nor can I remember how I was misled— I find I can act on this muscle myself, now that I know the corners of the mouth have to be drawn back— I know of case of man who can act on this muscle on one side, but not on the other, yet he asserts positively that both contract when he is startled.—⁴ And this leads me to ask you to be so kind as to observe, if any opportunity should occur whether the Platysma contracts during extreme terror, as before an operation; and secondly whether it contracts during a shivering fit.— Several persons are observing for me, but I receive most discordant results.—⁵

Pray accept my best thanks & apologies for this untidy letter, but I am not well today—

Dear Sir. | Yours very faithfully. | Ch. Darwin.

I beg you to present my most respectful & kind compliments to your honoured Father.⁶