But in the laws of "psychical hygiene," "liberty of movement" is not limited to a conception so primitive as that of merely "animated bodily liberty." We might, indeed, say of a puppy or a kitten what we say of children: that they should be free to run and jump, and that they should be able to do so, as in fact they often do, in a park or a field, with and like the children. If, however, we wish to apply the same conception of motor liberty to our treatment of a bird, we should make certain arrangements for it; we should place within its reach the branch of a tree, or crossed sticks which would afford foothold for its claws, since these are not designed to be spread out on the ground like the feet of creeping things, but are adapted to gripping a stick. We know that a bird "left free to move" over a vast, illimitable plain would be miserable. How then is it that we never think thus: if it be necessary to prepare different environments for a bird and a reptile in order to ensure their liberty of movement, must it not be a mistake to provide the same form of liberty for our children as that proper to cats and dogs? Children, indeed, when left to themselves to take exercise, show impatience, and are prone to quarrel and cry; older children feel it necessary to invent something whereby they may conceal from themselves the intolerable boredom and humiliation of walking for walking's sake, and running for running's sake. They try to find some object for their exertions; the younger children play pranks. The activity of children thus left to themselves has rarely a good result; it does not aid development, save as regards the physical advantage of general nutrition, that is, of the vegetative life. Their movements become ungraceful; they invent unseemly capers, walk with a staggering gait, fall easily, and break things. They are evidently quite unlike the free kitten, so full of grace, so fascinating in its movements, tending to perfect its action by the light jumping and running which are natural to it. In the motor instinct of the child there appears to be no grace, no natural impulse towards perfection. Hence we must conclude that the movement which suffices for the cat does not suffice for the child, and that if the nature of the child is different, his path of liberty must also be different. If the child has no "intelligent aim" in his movements, he is without internal guidance, thus movement tires him. Many men feel the dreadful emptiness of being compelled to "move without an object." One of the cruel punishments invented for the chastisement of slaves was to make them dig deep holes in the earth and fill them up again repeatedly, in other words, to make them work without an object.