Organic Connection Between Physical and Psychical 273 



This bare touch, so far as instances are concerned, of 

 overactivity in connection with reflexes, and especially with 

 instincts which are on the whole useful, leads naturally to 

 the great field of animal play. Space limitations prohibit 

 us from taking more than a bird's eye view of this field. 

 Fortunately, however, even such a view can be quite effective 

 for our purpose because of the well-known work of Karl 

 Groos, The Play of Animals. Our sole purpose here, as 

 in the rest of this discussion, is to answer the question 

 whether animals do or do not carry their activities which on 

 the whole are fundamental to their existence beyond what 

 is necessary for their own individual requirements. With 

 Groos's explanatory theory of play we are concerned only 

 so far as it involves the question of fact upon which our 

 present interest centers. That most if not all animal activ- 

 ity which can rightfully be called play, and which is not 

 intelligent, is instinctive, we believe Groos has conclusively 

 shown. The explanation adopted by Spencer and others 

 that play is the useless imitation by young animals of useful 

 activities performed by their seniors, the imitative acts be- 

 ing useless because merely the overflow of "surplus energy," 

 is certainly inadequate, as Groos has insisted. That animals 

 constantly go through performances playfully which they 

 have had no chance to see or to have otherwise impressed 

 upon them from without, is as certain as that they constantly 

 perform useful acts in this way. 



It consequently results that a source of energy for play, 

 that is, for actions which are not immediately essential to 

 the existence of the organism, must be an endowment of the 

 organism no less certainly than that a source of energy must 

 exist for actions which are essential to its existence. So 

 Groos's statement : "A condition of surplus energy still ap- 

 pears as the conditio sine qua non that permits the force 

 of the instincts to be so augmented that finally, when a real 

 occasion for their use is wanting, they form their own mo- 



