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, ete. 
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 
