16 ROYAL SOCIETY 0^^ CANADA 



for tluiii. Mv experiments show that in dog>, eats and rabbits the eor- 

 tcx is inexcitable at birth and for some days afterwards ; that the same 

 applies to the white matter, so that if by "newly-born"' Soltmann means 

 animals just l>orn or only a few days (two to four) old, 1 cannot agree 

 with him : but he is correct in stating that the Avhite matter is, as a rule, 

 earlier functionally active than the cortex. To these remarks, as I have 

 shown, the cavy is an exception, as its cortex responds to stimulation at 

 or a few hours after birth. 



While in the rabbit and the cat my experiments show already that 

 tbe centre for the fore-limb is responsive before that for the himl-hmb, 

 this does not apply to my experiments on dogs. It can scarcely be an 

 experimental coincidence that in by far the greater number of my cases 

 the hind-limb in dogs was the tirst to react. It may, however, be that 

 this divergence from Soltmann's results is to be explained by individual 

 differences. 



I am very glad to find Soltmann recognizing differences for " indi- 

 viduals and races " as regards the exact site of early localization. I am 

 certain that this individually applies not only to this point, but also to 

 the date at which the centres tirst became functionally active, etc., and 1 

 strongly suspect that in dogs there is no fixed rule as to which limb tirst 

 responds to electrical excitation of the cortex. It must be borne in mind 

 that the fore-limb is much more and much earlier used well by the 

 rabbit and the cat than by the dog. 



My results are also in entire agreement with those of Soltmann, in 

 that they show that the centres for the face and neck are of later 

 development than those for the limbs, though in the case of the rabbit 

 there is very little, if any, difference as regards the face and the fore- 

 limb. 



Soltmann's work on ablation of the cortex, carried out under great 

 difficulties, as I well know from experience (for. as he points out, the 

 mother interferes in a most troublesome way with the wound), are quite 

 in accord with m}- results as far as they go, i. c, ablation of the cortex 

 does not lead to paralj'sis or any decided alterations in the movements of 

 very 3'oung animals. 



Soltmann is also correct in stating that localizati(jn is at first some- 

 what indefinite, but gradually gets better defined. 



I have also found, as he states, that stimulation of an area lying 

 between, .say that for the fore-leg and that for the hind-limb, gives rise to 

 movements of both legs. This is not, however, a ver}" frequent result 

 with weak currents and is still rarer in animals in which tlie localization 

 is well defined. 



In some cases in my experience, as noted in using a strong current, 

 both limbs move together and perhaps also the head. No doubt, ditter- 

 cnce of current ma}' explain some of these 3ases. Occasionally both 



