[mills] functional DEVELOPMENT OF CEREBRAL CORTEX ir 



forc-liml)S move on stimulating one side of (he hrain. It is more ditfieult 

 to explain this by ditt'usion from the use of any moderate current. 



The advance in the readiness with which a centre can be stimuhited 

 noticed in my record of cases seems to me to indicate in the clearest way 

 that there is a process of development in the bi"ain cortex. When the 

 centre is less developed it requires a sti'onger stimulus, in some instance* 

 a ver}^ strong one, and it is not satisfactor}- to assume that when on 

 stimulating the cortex no result follows till a strong current has been 

 used that the result is owing to diffusion of current unless it can be 

 shown that in the same subject the white matter i-eacts easier, and as 

 this has not been my experience in many instances on very young 

 animals, I have been strongly impressed with this gradual development 

 of centres, rapid as it is. The difficulties in the cases just referred to will 

 not be entirely removed until the histological development of the l)raini 

 is better worked out. 



As Dr. Ferrier's work ' is so well known, I quote in part the para- 

 graph which bears on this subject of the earl}- condition of the coitex : 

 " It is not until after the opening of the eyes — usually about the eighth 

 day in dogs — that the limbs can be excited to action by electrical 

 stimulation of the sigmoid gyrus. Generally the cortical centres do not 

 react till about the tenth day, the centres for the fore-limb becoming 

 excitable before those of the posterior limb. Similar conditions obtain 

 in rabbits and guinea-pigs.'' 



Opening of the eyes on the eighth day in dogs must be of the rarest. 

 It seldom occurs before the tenth to the thirteenth day. It is, however 

 quite correct that in dogs the cortex is rarely, if ever, excitable before- 

 the eyes do open. 



I, as already stated, have not found that in dogs the centre for the 

 fore-limb is the first to develop, so that this statement must be modified. 

 The guinea-pig (cavy) must also be excluded from Ferrier's generalization.. 



I think my researches are the only ones carried out in connection 

 with an extensive study of the psychic'- development of the same 

 creatures, and that more groups of animals have been compared than by 

 any previous investigator. 



I give below the conclusions that I believe ma}^ be relied on as 

 regards the functional development of the brain in the dog, the cat, the 

 rabbit and the cavy. As to rats and mice I must express mj^self with, 

 more hesitation. 



Though I have made a series of experiments on the domestic f<jwl 

 and the pigeon, chiefly the latter, I have never been able to get move- 

 ments of any part (the eyes excepted) on stimulating the cortex in 

 mature animals, consequently did not try young ones. I believe the 



1 The Functions of the Brain, second edition. London, 1886. 

 '^ See these Transactions for 1894 and 1895. 



Sec. IV., 1896. 2. 



