14 KOYAL SOCIETY OF CANADA 



In a cavy, twenty-six to thirt}' hours utter birth, I liad no diilic-ulty 

 in getting movements of both the fore-limb and the hind-limb with a eur- 

 rent of very moderate intensif}'. 



In a cavy eight days old, movements of the limbs, head (to opposite 

 side) and eyes almost, if not quite, as perfect as in older specimens. 



y. — The E.\t and the Mouse. 



I have been able to make but few experiments on young rats and 

 mice, but, so far as they go, they point clearly to the same conditions as 

 in the rabbit, i. e., while their eyes are unopened the cortex is inexcitable, 

 but very soon after the rever.se. Eats, mice and rabbits are born naked 

 (comparatively hairle.ss), and with closed eyes, but both develop i-apidly, 

 phvsically and psychically when the e3-es do open. 



EejMarks on the Experiments Made on Eabbits. 



Cases I. and II. show that it is some time before there is any distinct 

 reaction to stimulation of either the corte.x; or the medulla, 



( 'a.se 111. seems to be a clear instance of cortical localization, and 

 that head (neck) and face movements should be induced thus early is 

 noteworthy. 



Case IV. points to earlier development in the mediilla. 



Case V. illustrates the late development of the cortex and indicates 

 that in this case also the white matter is somewhat in advance. 



Case VI. seems to indicate an earlier development of the centre for 

 movement of the head and advance in the medulla over the cortex. 



Neither in these noi- in older rabbits have I been able to get move- 

 ments of the hind leg on stimulation of the cortex under the same circum- 

 stances as those under which the centres for other movements reacted. 



Eemarks on the Experiments Made on Other Eodents. 



The ^'ar/y.— There is little additional to be said. It is plain, from the 

 sample experiments reported, that the motor centres in this animal, at all 

 events the principal ones, are practically functionally active at birth, 

 though there is a progressive development of a kind reaching a high 

 degree oï perfection when the animal is but a few days old. 



Jiats and J//c<?.— They seem, so far as the brain is concerned, to 

 develop in the same way as the rabbit, all three groups contrasting 

 strongly with the cavy. 



Conclusions Eegarding Eodents.— Comparisons. 



In rabbits, rats and mice the cerebral cortex is not functionally active 

 at birth, nor long, il' ut ull, before the eyes open. 



The early development of the cortical centres presiding over the 

 movements of the head, as a whole, and of its different muscles, is a 



