THE PSYCHIC DEVELOPMENT OF YOUNG ANIMALS 169 
and the body must be studied together will, I am satis- 
fied, become more and more evident as investigations 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 measuring most of 
them, and it is more than difficult to express much of 
what is observed in a way to make it appreciable by 
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 contemporaneous 
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 development? In 
itself the direct causal relation from increasing experi- 
ence 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. 
