THIî PSYCinc DKVq-^LOPMKNT OF YOUX(i ANIMALS 59 



Periods of Development. — A study of the diary will show that the two great periods are : 

 that before the eyes are open and that succeeding this one. The time between the opening 

 of the eyes and the establishment of real vision and hearing constitutes a transition or inter- 

 mediate period. 



Development is very slow in the first period and existence almost a vegetative one, yet 

 not wholly so for by the skin, the muscular sense, to some extent by taste and smell, by 

 visceral sensations, etc., the animal's nervous centres are being modified. 



The intermediate period is marked by a considerable advance, though slow as compared 

 with the progress made within the next few days. 



The period between about the 17th and the 45th day is that of greatest importance in 

 the life of the dog. 



After that there is constant improvement from experience up to the 60th day, and this 

 is well marked — more so than at any later time ; but it is not of equal importance with that 

 preceding. 



These periods glide into one another and many others might be interpolated, but I 

 desire to avoid artificiality which is sure to result from the attempt at numerous divisions of 

 any kind. 



There is not the sharp line of différence between the dog and other animals before the eyes 

 are opened and afterwards, which some writers would have us believe, though between the 

 animal when it can neither see nor hear and the same animal ten days afterwards, there is 

 indeed a vast diflference. But as to the rate and nature of development the reader may draw 

 his own conclusions 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 more- 

 over that the whole difterence 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 presented 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 recognize 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 

 recognized 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 p.sychic status, I am not aware that anv 

 complete and systematic study of the subject has been attempted. That the mind and the 

 body must be studied together, will I am satisfied become more and more evident as investi- 

 gations on the one independently of the other prove disappointing. This applies more 

 particularly no doubt to the mind, but not wholly. While to a practised observer very many 

 shades of change in physical developments may be observed, there is no good method of 



