The case is described of a young woman who presented an absolutely different personality according to whether or no she was in a state of morphinomania. At the age of twenty-three, while on board a ship, she first became addicted to morphia, and for the next few years she was alternately well and morphinomaniac, presenting with each phase a characteristic and markedly different personality. While taking morphia she was sedentary, calculating, most careful of her affairs, endowed with a wonderful memory, logically minded, and she showed an absence of affection. When cured of her morphia habit, on the contrary, she ceased to care about her affairs, was liberal, extravagant, heedless of the future; her affective side was in evidence. It would almost seem as if in this case morphia produced an inhibition of the affective centres, permitting of a preponderating action on the part of the intellectual faculties.