168 ANIMAL INTELLIGENCE 



hear, and the same animal ten days afterwards, there is 

 indeed a vast difference. But as to the rate and nature 

 of development the reader may draw his own con- 

 clusions, and to enable him to do so has been my chief 

 object in giving a record of facts so detailed and as free 

 from gaps and omissions as possible. I am convinced, 

 moreover, that the whole difference in the periods referred 

 to is not to be referred merely to the presence or absence 

 of vision and hearing. 



About this time the whole nature of the animal seems 

 to undergo a comparatively sudden leap forward in 

 advancement, possibly as the result of the accumulated 

 experiences of ages acting through heredity I mean 

 that the advances directly referable to the advent of 

 seeing and hearing would tend to accumulate by 

 heredity, and to be expressed in the organism in time 

 in a more decided manner. 



GENERAL. The preceding are a few of the many 

 aspects of the psychic (and physical) development pre- 

 sented within the first sixty days of existence of puppies. 

 I deprecate hard and fast lines of demarcation in biology 

 and psychology, believing that in nature one thing, as a 

 rule, glides into another at some stage of development, at 

 all events. My commentary on the diary is, therefore, 

 not claimed to be complete, if indeed it is possible 

 to recognise all that there is in psychic development, 

 however closely one may observe, however perfectly 

 analyse. 



PHYSICAL CORRELATION. Already, for some years, the 

 relations of mind and body have been recognised in a 

 general way, and studied with results of definite value ; 

 but while there have been isolated experiments and 

 observations made on young animals bearing on the 

 relation between physical development and the psychic 

 status, I am not aware that any complete and systematic 

 study of the subject has been attempted. That the mind 



