This affection is, with very few exceptions, confined to the female sex, and that principally during adolescence, usually heralding some disturbance of menstrual function, but chiefly characterized by deficiency of hemoglobin of the blood. It seldom affects early childhood, and if so, is usually connected with precocious development of sex. It is also seldom seen after the thirtieth year, but is by far most common at the beginning of puberty. It is also claimed to be at times hereditary, or apparently so. Sedentary occupation, indoor life, unsuitable food, excessive physical and mental activity, emotional or psychic disturbances are all causative in the majority of cases of chlorosis. It is remarkably frequent in girls who menstruate prematurely, indeed, one can usually predict a case of chlorosis in girls whose first menses appear very early. Often this affection is associated with anemia, coexisting or following soon in its wake. Careless observers may make a mistake in diagnosis, though this is one of the most easily diagnosticated of all diseases.