272 ANIMAL INTELLIGENCE 



can be made manifest by our crude methods of experi- 

 ment. 



A very marked feature in the psychic development 

 of the cat is the early appearance of the play instinct,* 

 and the perfection of the fore-limb in carrying out the 

 movements necessary for its manifestations. The cat 

 has incomparably better use of the fore-limb at an 

 early date. I have recorded observations on play 

 (with use of the paws) as early as the 22nd day, and, 

 as is well known, the kitten and the older cat have a 

 variety and perfection of movement of the fore-limb 

 never acquired by the dog. This is distinctly corre- 

 lated with brain development, for, as I have pointed 

 out, movements of the fore-limb are in the cat the first 

 that can be induced by electrical excitation of the 

 cortex, and to this observation my experience leads me 

 to believe there are practically no exceptions, while 

 the case is very different for the dog. Some investi- 

 gators have expressed the opinion that the fore-limb is 

 also the first to respond in the dog, but this does not 

 accord entirely with my experience. It has occasion- 

 ally been so in the puppies on which I experimented, 

 but in the large majority the hind-leg responded first. 

 Mongrels and pure-bred animals of different varieties 

 were used. I do not therefore believe that the state- 

 ment that the fore-leg in the dog is always the first to 

 respond to electrical excitation, can any longer be main- 

 tained as a sound generalisation, but it may be, as I 

 have suggested in my paper on the brain, that the 

 truth is, that sometimes the one and sometimes the 

 other limb is the first to react, and that large allowance 



* The whole subject of play in animals is exhaustively treated by 

 Dr Karl Grooa in his "Die Spiele der Thiere," Gustav Fischer, 

 Jena, 1896, which has been translated into English, with additional 

 notes by the German author. 



