156 ANIMAL INTELLIGENCE 
the mouth is naturally assisted by the forelimbs. As 
locomotive power increases, the puppy takes to walk- 
ing away and returning to the attack, then running, 
jumping, etc. i 
Soon he begins to shake objects, pull at them, 
tear them. My observations show conclusively that 
the movements in play appear in the order of the 
final perfection of the co-ordinated movements of the 
animal as represented, so far as the nervous system 
is concerned, in the cerebral cortex by well-defined 
centres. I am now, and for some time have been, 
engaged upon experiments which show that the 
cortical brain centres do not all develop at the same 
time, but in a certain order, a fact which throws a flood 
of light on the psychic, as well as the physical, 
development of animals. 
The pleasure of play is that of movement at first. 
Later, there is no doubt a psychic complexity of feeling 
not known to the very young puppy. 
Nevertheless, the observations reported on the 26th 
and 33rd days would seem to indicate that even at 
this early age the puppy has some sense of fun or 
humour. 
SCRATCHING.—I have endeavoured to note the earliest 
attempts at this act, and give some details from time 
to time, as it illustrates several points. 
I should be disposed to regard scratching as a 
hereditary reflex perhaps, as is illustrated by the 
experiment of the 17th day. In other cases, how- 
ever, the element of will does enter more or less into 
this act. Even an adult dog will move his leg in the 
air in harmony with scratching irritation against his 
side—a pure reflex. When, as noted on the 40th 
day, the puppy turns his neck so as to adapt the 
movements of the leg, and the position of the parts 
to be scratched, it is plain that we have here the 
