The body of the child is moulded and shaped by the environment in which it grows.  Pure air, a rational diet, free movement, give strength and symmetry to every part.  Faults of hygiene debase the type, although the type is determined by heredity which in the individual is beyond our control.  Mothers and nurses to-day are well aware of the need for a rational hygiene.  Mother-craft is studied zealously and with success, and there is no lack of books to give sound guidance and to show the mean between the dangerous extremes of coddling and a too Spartan exposure.  Yet sometimes it has seemed as if some mothers whose care for their children’s physical health is most painstaking, who have nothing to learn on the question of diet, of exercise, of fresh air, or of baths, who measure and weigh and record with great minuteness, have had their attention so wholly occupied with the care of the body that they do not appreciate the simultaneous growth of the mind, or inquire after its welfare.  Yet it is the astounding rapidity with which the mental processes develop that forms the distinguishing characteristic of the infancy of man.  Were it not for this rapid growth of the cerebral functions, the rearing of children would be a matter almost as simple and uneventful as the rearing of live stock.  For most animals faults of environment must be very pronounced to do harm by producing mental unrest and irritability.  Thus, indeed, some wild animal separated from its fellows and kept in solitary captivity may sicken and waste, though maintained and fed with every care.  Yet if the whole conditions of life for the animal are not profoundly altered, if the environment is natural or approximately natural, it is as a rule necessary to care only for its physical needs, and we need not fear that the results will be spoiled by the reaction of the mind upon the body.  But with the child it is different; airy nurseries, big gardens, visits to the seaside, and every advantage that money can buy cannot achieve success if the child’s mind is not at rest, if his sleep is broken, if food is habitually refused or vomited, or if to leave him alone in the nursery for a moment is to evoke a fit of passionate crying.

The grown-up person comes eventually to be able to control this tremendous organ, this brain, which is the predominant feature of his race.  In the child its functions are always unstable and liable to be upset.  Evidence of mental unrest or fatigue, which is only rarely met with in grown persons and which then betokens serious disturbance of the mind, is of comparatively common occurrence in little children.  Habit spasm, bed-wetting, sleep-walking, night terrors, and convulsions are symptoms which are frequent enough in children, and there is no need to be unduly alarmed at their occurrence.  In adult age they are found only among persons who must be considered as neuropathic.  To make the point clear, I have chosen examples from the graver and more serious symptoms of nervous unrest.