Habit in producing constitutional peculiarities, and use in strengthening, and disuse in weakening and diminishing organs, appear in many cases to have been potent in their effects.
Badirudi aztura, osaerako berezitasunak sortaraziz, erabilera, organoak sendatuz, eta erabilerarik eza makalduz eta murriztuz, kasu askotan indartsuak izan direla beren ondorenetan.