Innumerable illustrations for these classes of movements suggest themselves. A piece of bread put on the back of the tongue is moved down the esophagus by the proper muscular contractions. A particle moving into the wrong passage is thrown out again by coughing. If the palm of an infant is gently stroked, the hand closes and takes hold of the stroking finger. If the palm is scratched, the hand quickly recedes. A mild and steady light attracts the child’s eye, which follows the movements of the light. From an intense and flickering light the eye turns away. A piece of sugar is kept in the child’s mouth and moved about by the tongue until it is dissolved. A bitter root causes the lips to recede and the tongue to make a pushing movement. If the child is hungry, he cries, kicks, and strikes out with his arms until he is fed. After being fed he lies still so that digestion is not interfered with by the blood being drawn into the peripheral parts of the body. Movements which do not serve self-preservation so directly are called play. When a cat perceives a mouse, she jumps at it and catches it. But before eating it, she usually lets it loose and catches it again, and so on several times. When she finds a ball of yarn, she treats it similarly, although she must know that it is not edible. A dog gnaws a bone because this contributes to his nutrition. But he also gnaws table legs and rugs, although these have no nutritive value. He chases rabbits and other small animals which he can eat. But he chases no less eagerly other dogs, wagons, cyclists, horses, none of which serve as articles of food for him. The same is true for man. The infant’s kicking, the small child’s breaking of his toys, do not have any immediate value. Men and animals respond to things not only by fighting, but also by play. The significance of playful movements is to be found in the exercise, the development, and the conservation of the abilities given to them by nature. As in the movements of self-preservation, so in play pleasantness and unpleasantness make their appearance. Extensive exercise of natural abilities is highly pleasant, enforced inactivity equally unpleasant.