In primitive warfare the action of the participants was homogeneous; that is, each combatant performed the same kind of service as did every other combatant and largely on individual initiative. The "clash of battle and the clang of arms" meant an individual contest for every man engaged. In contrast to this there is, in modern warfare, a distribution of functions, some combatants performing one kind of duty and others another, all working together to the common end. In the higher team organizations of Basket Ball, Baseball, Football, there is such a distribution of functions, some players being forwards, some throwers, some guards, etc., though these parts are often taken in rotation by the different players. The strongest characteristic of team play is the coöperation whereby, for instance, a ball is passed to the best thrower, or the player having the most advantageous position for making a goal. A player who would gain glory for himself by making a sensational play at the risk of losing for his team does not possess the team spirit. The traits of character required and cultivated by good team work are invaluable in business and social life. They are among the best possible traits of character. This class of games makes maximal demands upon perceptive powers and ability to react quickly and accurately upon rapidly shifting conditions, requiring quick reasoning and judgment. Organization play of this sort begins to acquire a decided interest at about eleven or twelve years of age, reaches a strong development in the high schools, and continues through college and adult life.

Such are the main characteristics of the games which interest a child and aid his development at different periods. They are all based upon a natural evolution of physical and psychological powers that can be only hinted at in so brief a sketch. Any one charged with the education or training of a child should know the results of modern study in these particulars.

The fullest and most practical correlation of our knowledge of the child's evolution to the particular subject of play that has yet been presented is that of Mr. George E. Johnson, Superintendent of Playgrounds in Pittsburgh, and formerly Superintendent of Schools in Andover, Mass., in Education by Plays and Games. The wonderful studies in the psychology of play by Karl Groos (The Play of Animals and The Play of Man), and the chapter by Professor William James on Instinct, show how play activities are expressions of great basic instincts that are among the strongest threads in the warp and woof of character—instincts that should have opportunity to grow and strengthen by exercise, as in play and games. We have come to realize that play, in games and other forms, is nature's own way of developing and training power. As Groos impressively says, "We do not play because we are young; we have a period of youth so that we may play."

The entire psychology of play bears directly on the subject of games. Indeed, although the study of games in their various aspects is of comparatively recent date, the bibliography bearing on the subject, historic, scientific, psychologic, and educational, is enormous and demands a distinct scholarship of its own.

It is highly desirable that a teacher should know the significance of certain manifestations in a child's play interests. If they should not appear in due time, they should be encouraged, just as attention is given to the hygiene of a child who is under weight for his age. But it should not be inferred that any hard and fast age limits may be set for the use of different plays and games. To assign such limits would be a wholly artificial procedure, and yet is one toward which there is sometimes too strong a tendency. A certain game cannot be prescribed for a certain age as one would diagnose and prescribe for a malady. Nothing in the life of either child or adult is more elastic than his play interests. Play would not be play were this otherwise. The caprice of mood and circumstance is of the very soul of play in any of its forms.

The experience of the writer has been chiefly away from dogmatic limitations in the use of games. Very young players and adults alike may find the greatest pleasure and interest in the same game. Previous training or experience, conditions of fatigue, the circumstances of the moment, and many other considerations determine the suitableness of games. To illustrate, the author has known the game of Three Deep, which is one of the best gymnasium games for men, to be played with great interest and ability by a class of six-year-old boys; and the same game stupidly and uninterestedly bungled over by a class of much older boys who had not had previous training in games and were not alert and resourceful. Similarly, the comparatively simple game of Bombardment may be interesting and refreshing for a class of tired business men, while high-school pupils coming to care largely for team play may prefer Battle Ball, a more closely organized game of the same type. In general, boys and girls dislike the mode of play they have just outgrown, but the adult often comes again to find the greatest pleasure in the simpler forms, and this without reaching second childhood.