Evidently, then, physical conditions do not of themselves account for nightmares and night terrors. One must look elsewhere for their ultimate cause. This is what the medical psychologists have done, and, doing this, they have discovered that the children who are troubled by night terrors are always children of a sensitive nervous organisation who have been subjected to emotional stress. A child may be nervously highstrung, yet entirely escape night terrors, provided his mind be kept free from emotional upheavals. But let anything occur to disturb him emotionally in an excessive degree and he at once becomes likely to suffer, not only from night terrors, but also--as it has been a prime purpose of this book to impress convincingly on every reader--from nervous affections of a more serious kind. He may even have "day terrors," seeing imaginary and terrifying objects as vividly as the child who wakes in panic from a distressing dream. For example, a boy of eight was sent to the Washington neurologist, Doctor T. A. Williams, to be treated for general nervousness, and, in particular, for a tendency "to see things where there is really nothing to be seen." Doctor Williams found the boy to be so nervous that it was hard for him to sit still and to keep from wriggling excitedly about in his chair. Questioned as to his hallucinations, he said that these were mostly of a snake. He could not describe the imaginary snake, except to say that its head was like an eel's. It seemed to come from nowhere, and presented itself to his astonished gaze with a suddenness that caused him to scream and run. His father gave Doctor Williams the additional information that these hallucinations were experienced only when the boy was alone, and that, though his day terrors were not followed by night terrors, he would not go to bed unless some one were in the room with him. Questioning his little patient more closely, Doctor Williams next learned that he had a veritable horror of being alone at any time. As long as somebody was in sight, he could enjoy his games, and would readily run errands. Left alone, the imaginary snake, or some hallucinatory wild beast, was almost at once seen by him. Further inquiry brought out the significant fact that this fear of solitude had actually been implanted in the boy by over-anxiety on his mother's part.