William James, The Principles of Psychology, Volume 1…
“ The central part of the me is the feeling of the body and of the adjustments in the head; and in the feeling of the body should be included that of the general emotional tones and tendencies, for at bottom these are but the habits in which organic activities and sensibilities run. Well, from infancy to old age, this assemblage of feelings, most constant of all, is yet a prey to slow mutation. Our powers, bodily and mental, change at least as fast. ”
