THE FUNCTIONAL DEVELOPMENT OF THE 
CEREBRAL CORTEX IN DIFFERENT 
GROUPS OF ANIMALS. 
In connection with my investigations on the psychic 
development of young animals,* it seemed important, 
in regard to the question of physical correlation, to 
ascertain, in so far as that is possible by experimental 
methods, at what period the cortex of the brain becomes 
functionally active. Nothing, to my knowledge, has 
been done of late years on this subject. I determined, 
therefore, to give it as complete an investigation as 
possible. Realising that breadth of investigation was 
important, as well as thoroughness, the experiments 
have not been confined to one or two groups of animals, 
but cover several. This, together with the desire to 
report only what was thoroughly well determined, has 
extended these investigations over a long period and 
involved much labour. 
Only those individual animals have been used the 
exact age of which was known, and, as a matter of 
fact, most of them were born and kept under my own 
observation, so that their exact age and, in many cases, 
their breeding, etc., were known. It is scarcely neces- 
sary to state that the experiments were rendered 
painless. 
* The author has thought it well to introduce here just so much of 
this paper as will make the following one somewhat clearer. Both 
appeared in the first instance in the Zvransactions of the Royal 
Society of Canada, in 1896. 
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