Doctor Williams' patient was a ten-year-old girl, the daughter of a clergyman. She had been lovingly reared, and until the age of nine had been easy to manage, vivacious, and happy. Then there came a marked change in her behaviour. She became easily irritated, had frequent crying spells, and frequent fits of sulkiness. Besides this, she had difficulty in studying. Thinking that she had been overworking, her parents took her out of school, although her mother noticed that she was less inclined to sulk when kept busy. What Doctor Williams found, after a long and careful examination of the girl and questioning of her parents, was unmistakable evidence of nerve deficiency, due chiefly to faulty diet, and aggravated by "parental interference, well meant, but entirely injudicious." She had been eating oatmeal and meat to excess, had been taking her principal meal at night, and had gone to bed soon after it. Doctor Williams ordered that her allowance of meat and oatmeal be cut down, that she eat her principal meal at noon, and that she stay up for at least an hour after her evening meal. Further, he gave these directions: "On waking in the morning, the child must make a practice of getting up at once, instead of ruminating in bed. Parents must avoid criticising her about trifles, and her behaviour must be left to take care of itself at present. Her affections should be indulged and reciprocated. She must be given plenty to do and sent back to school in a few days." Under this treatment the girl's disposition began immediately to improve. Within two weeks her mother reported to Doctor Williams that she was as "happy and joyous" as she had formerly been. No longer was her stomach being loaded with food it could not digest; and with the removal of this source of toxic irritation, together with the suggested changes in her parents' handling of her, she had become a different child. On the other hand, underfeeding may be, and often is, a cause of sulkiness, owing to the inadequate nourishment the underfed child's brain receives and the general weakness of his system. Sulkiness, again, may be associated with an insufficiency of physical exercise, or with failure to make sure that the child's living and sleeping quarters are properly ventilated. Fresh air is as essential as digestible food to the maintenance of nervous balance. When, as sometimes happens, children are obliged to spend their school hours in dusty, ill-ventilated classrooms, when they return to homes with few windows, and these seldom open, and when they sleep in a tainted, vitiated atmosphere, it is indeed hard for them to see life in bright colours. Besides which, to prevent or cure sulkiness in a child, it is not enough to keep school and home well ventilated, and let the child play outdoors as much as possible. It is necessary also to see to it that the child is so conditioned that he will have no difficulty in adequately breathing the fresh outdoor air.