Play has been called the ideal type of exercise, because it is the kind of exercise that occupies the whole child, his mental as well as his physical side--and later, also, the moral side. In play the exercise is regulated by the interests, so that, while there may be extreme exertion, there is not the same danger of overstrain as is possible with work that he is forced to do. In play the exercise is carried on with freedom of the spirit, so that the flow of blood and the feeling of exhilaration make for health.