THE SURPLUS ENERGY THEORY OF PLAY. 23 



velop them. We know that all animals have a tendency 

 to make use of a certain amount of energy, determined 

 not by the accidental needs of the individual, but by the 

 needs of the species in general." But if this is the case, 

 play itself is not merely a result of the accidental needs 

 of the individual, but rather an effect of natural selec- 

 tion, which works for anything that is serviceable for 

 the preservation of the species. The observation of the 

 different kinds of play is sufficient to establish this. 

 Most plays of young animals — and it is this that must 

 always present the essential problem in a theory of play 

 — act for the preservation of the individual, all for the 

 preservation of the species. At the same time the natu- 

 ral — that is, the self-originated — plays of human beings 

 are to be considered as practice that is useful not only to 

 the individual, but also to the race. '^ Pro patria est, 

 dum ludere videmur " is the motto that Guts Muths has 

 placed in the front of his book. 



Can a phenomenon that is of so great, so incalculable 

 value possibly be simply a convenient method of dis- 

 sipating superfluous accumulations of energy? In all 

 this there seems nothing to hinder the assumption that 

 the instincts operative in play, like so many phenomena 

 of heredity, first appear when the animal really needs 

 them. Where, then, would be the play of the young? 

 It would not be provoked either by overflowing nervous 

 energy or by the need for recreation. Yet the early 

 appearance of this instinct is of inestimable impor- 

 tance. Without it the adult animal would be but poorly 

 equipped for the tasks of his life. He would have far 

 less than the requisite amount of practice in running 

 and leaping, in springing on his prey, in seizing and 

 strangling the victim, in fleeing from his enemies, in 

 fighting his opponents, etc. The muscular system would 

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