18 KOYAL SOCIETY OF CANADA 



statements of Ferrier^ lo the effect thai the cortex of the pigeon is 

 excitable to be erroneous. 



The brain of the bird will be further referred to in another paper. ^ 



General Conclusions. 



In the dog, cat, rabbit (and in .so far as the writer's experiments go 

 in the rat and the mouse) neither the brain cortex nor the underlying 

 white matter is excitable by electrical stimulation at birth or for some 

 days afterwards. 



The cortex is usually not excitable till about the period when the 

 eyes open, though there are exceptions to this rule, most frequent in the 

 writer's experience in the cat, in favour of an earlier date. 



The white matter of the brain just beneath the cortex is generally 

 excitable either at an earlier date than the cortex, or with a weaker stim- 

 ulus. 



The reaction for the limb movements is obtainable invariably some- 

 what earlier in the dog and the cat, and generall}' so in the rabbit, than 

 those for the neck, face, etc. 



Localization for the cortex and still more for the white matter is at 

 first ill-defined, but gradually, though rapidly, becomes more definite. 



In the cavy (guinea-pig) the cortex and the white matter beneath 

 are electrically excitable either at birth or a few hours afterwards, and 

 perfection of reaction and localization is reached in a few days. 



Before the brain coi'tex responds to electrical excitation, ablation of 

 the motor area (centres) leads to no appreciable interference with move- 

 ments. 



The younger the animal the stronger the current required to produce 

 reaction up to the time that localization is well established, i.e., the weak- 

 ness of the current required to cause a movement is an indication of the 

 degree of development of the centre in question. 



Differences for breeds and individuals exist and constitute to some 

 extent exceptions to the above general statements. 



In the above " cortex " refers to the gray matter in or near the motor 

 area and " white matter " to the brain substance immediately beneath. 



' The Functions of the Brain, second edition, London, l!^8(i, p. 262. 

 - These Transactions, 1896. 



