They occur in Darwin's Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), and in Huxley's Evidence as to Man's Place in Nature (1863).
These instances can be found within Darwin's Descent of Man (1871) and The Expression of the Emotions in Man and Animals (1872), as well as in Huxley's Evidence as to Man's Place in Nature (1863).