Sec. IV., 1890. [ 3 ] Trans. R. S. C. 



T. — T/ie Fanetional Development of the Cerebral Cortex in Different 



Groups of Animals. 



By Wesley Mills, M.A., M.l)., F.R.8.C., 



Professor of Physiology in McGill University, Montreal. 

 (Read May 20, 1896.) 



In connection with my investigations on the ps^^chic development o 

 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 ; accordingly I have lost no opportunit}' during the past two to 

 three years to secure the iiewly-boi'n young* of several groups of animals, 

 being those usually kept in confinement or inhabiting our dwellings. Eeal- 

 izing that breadth of investigation was important, as well as thorough- 

 ness, 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. 



Methods, 



Only'thoso 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. 



Anaesthetics. 



Anaesthetics were used in all cases, and invariably by inhalation, as 

 by this method alone can nice gradations in the depth of the anœsthesia 

 be made in young animals. The young animals of all the species that 

 have been the subjects of my experiments have taken anaesthetics well — 

 much better, in fact, as a rule, than the adults of the same groups. 



Throughout, ether has been used, as the most satisfactory, for sev- 

 eral reasons, it is safer, though in the case of the young animal this 

 applies with less force than for older ones But it is, to my mind, the 

 most desirable, chiefly because the degree of ana'sthesia can be so quickly 



1 Transactions of the Royal Society of Canada, 1894 and 1895. 



