THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 173 



change in the environment, indicating that experience, 

 even in the earliest days, is not lost on them. In other 

 words, the environment does and must act on the 

 nervous system, with results that manifest themselves 

 if in no more definite way, at least in this : that new 

 experiences (stimuli) cause comfort or discomfort, as 

 evidenced by quiescence or wriggling, cries, etc. 



Co-ordinated muscular movements appear in greatest 

 perfection in a certain order, viz. mouth and head 

 parts, fore-limbs, hind-limbs, tail, etc. 



These seem to be related to the order of development 

 of the centres of the cerebral cortex. 



The epochs most differentiated from each other in 

 the psychic and somatic life of the dog are (1) that 

 prior to the opening of the eyes, and (2) that subse- 

 quent to this event. 



The former suggests intra-uterine life by its negative 

 character, and is well marked off from the period that 

 follows, the more numerous avenues of knowledge exist- 

 ing, and their utilisation, and in other respects not well 

 understood, of the latter period. In other words, the 

 animal, after this period, can come more fully in con- 

 tact with environment, with corresponding results in its 

 development. It seems, besides, more impelled to do 

 so ; there is more vim in its whole nature. A transi- 

 tion period between the time when the eyes and ears 

 begin to open, and when the animal actually sees 

 objects and hear sounds, may also be recognised. 



The era of most rapid and most important develop- 

 ment is subsequent to the period when seeing and 

 hearing are established when the animal is in posses- 

 sion of all its senses, etc. This extends between the 

 20th and the 45th day approximately. 



Suggestive action, beginning perhaps with the first 

 manifestations of .the play instinct, has, especially as 

 time passes, a very important share in determining the 



