60 WESLRY MILLS ON 



measuring most of them ; and it is more than tliffieult to express much of what is observed 

 in a way to make it appreciable b}' the mind of the reader. 



Until our knowledge of the relations between the mind and the body — between the 

 history of the body and that of the mind — between ontogeny and psychogeny (psychogenesis) 

 is made very much more complete, it would appear that it is desirable that a contemporane- 

 ous account be kept of every change of whatever kind observed both physical and psychic. 



We dare scarcely say that matters so apparently trivial as the change in colour of the 

 iris, or as the pigmentation of the nose for example are in no relation whatever with 

 psychic development. 



Has the eruption of the teeth in the puppy no relation to psychic growth and develojD- 

 ment ? In itself the direct causal relation from increasing experience thus afforded by their 

 use is not all ; and there is doubtless in this more than we are in a position to define as yet- 

 As soon as the teeth appear and the jaws are more used as is now the tendency the puppy 

 advances in consequence of this very use of teeth and jaws, but this is probably not the 

 whole story. 



From the chief diary and the comments on it the reader will be able to cull many 

 instances of psychic and physical correlations. Between the physical changes in the eye and 

 ear especially and the psychic results the closest relation is evident, and this should suggest 

 that similar close connection exists elsewhere. "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 alwaj's 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 according 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 difierences in develop- 

 ment in the various breeds of dogs. 



I found that the litter of Bedlington terriers developed much faster psychically than St. 

 Bernards, and they also mature earlier, physically and otherwise, a remark that applies to 

 the smaller breeds of dogs generally. 



They sooner show, especially in movements, a great superiority, which strengthens the 



