From Lucy Caroline Wedgwood [25 April 1870]1
Dear Uncle Charles
I have at last made out for certain that my dog does raise his lip on the side on which he is attacked, without raising it on the other.
I tried making a horse kick by whipping him behind when riding him several times and always with the same result: he just turned his ears round before kicking but never once laid them flat as before biting.2
The horse when I scratch him stretches out his nose, opens his mouth a little, and with lips parted &
Aggressive behaviour of dogs and horses.
Please cite as
Darwin Correspondence Project, “Letter no. 7174,” accessed on 12 February 2016, http://www.darwinproject.ac.uk/DCP-LETT-7174