170 ANIMAL INTELLIGENCE 



While the puppy sprawls in the blind period, he cannot 

 investigate objects, and we find, as the sensory organs 

 advance in development, the animal's locomotor power 

 increases, so that he can the better use all his senses, 

 hence the great strides he makes in development from 

 one part undergoing a change which adapts it to the 

 well-being of other parts and the entire organism. 



As a matter of fact, motor power is, in the young 

 animal, a very fair guide to its general advancement, 

 and in tracing the development of the puppy one notices 

 this daily. 



There is a certain order of progress : first the tongue 

 laps, etc., as in sucking ; then after the eruption of 

 teeth, use of the jaws at the same time ; and more so 

 later the movements of the fore-limb long, in fact 

 always, in advance of the hind-limb the tail soon 

 taking a share in the movements. 



These movements not only increase in power, but in 

 precision, i.e. they are co-ordinated, and this is well 

 illustrated by many facts stated in the diary. 



These movements, the development of the senses, 

 etc., etc., are of course impossible without the nervous 

 system, and they gain in precision and variety, accord- 

 ing to the rate and extent to which the cortex of the 

 cerebrum is developed into functional activity. My 

 own experiments on the brains of young animals are 

 not yet complete, so that I shall not here refer to them 

 further than to state that they bear out the view just 

 stated. During the blind period the cerebral cortex is 

 found to be unexcitable, while in the mature dog move- 

 ments of definite groups of muscles may be readily 

 obtained by stimulation of the cortex. 



DIFFERENCES IN BREEDS. Both physically and 

 psychically there are differences in development in 

 the various breeds of dogs. 



I found that the litter of Bedlington terriers 



