4 ROYAL SOCIETY OF CANADA 



vai'ied. This is a matter of great moment, seeing how sensitive the cor- 

 tex is to injury from exposure to the air, loss of blood, etc. It is unfor- 

 tunate that ether favours ha-morrhage perhaps more than some other 

 anu'sthetics. but I think the advantage just refen-ed to outweighs all its 

 disadvantages. 



01»jections to other methods of producing narcosis will be considered 

 later. 



Experience alone determines thai degree of anjesthesia in each ani- 

 mal which is most favourable for the experiment. During a certain 

 depth of anaesthesia it is impossible to get any response by electrical 

 excitation by an}'- reasonable strength of current ; on the other hand, all 

 my experience is against placing any reliance on results obtained from 

 animals when not under the influence of an anaesthetic to some extent, 

 the degree, as before mentioned, being determined by experience. If 

 there be a reaction from one part of the corte.x, one may assume, of 

 course, as a general rule, that the rest of the cortex is in an equally 

 favourable condition to respond, if it be natural for it to do so. 



Operative Procedure. 



It matters little, it has been found, how the brain is laid bare, j)ro- 

 vided it be not injured. I have generally opened the skull over a cer- 

 tain area with a trephine, and then proceeded to remove a sufllcienc}^ of 

 bone with a small bone forceps. In the case of very small and j^oung 

 animals a sharp knife and a dressing forceps were the only instruments 

 found necessary. 



Methods of Exa.aiination. 



In a few cases the area usuall}' responsive to electrical excitation ha^ 

 been removed, the wound carefully closed with regard to antisepsis, and 

 the young one returned to its mother. Eeference will be made to this 

 subject again. In by far the greater number of cases electrical excitation 

 of the cortex was the sole method employed to determine the question of 

 its functional activity. Of necessity, this can reveal only the ])resence or 

 absence of motor centres in a functionally active condition. While such 

 centres are known to be confined in the mature animal to certain dcflnite 

 regions of the cortex, in practice it was not found wise to limit explora- 

 tions to such areas, and, as a matter of fact, almost, if not quite, the whole 

 coi'tical surface of the cereljrum was inade the subject of examination. 



Apparatus Used. 



Only the rai)id]y interrupted cui-rent of a Du Jiois-I'eymond iuduc- 

 torium was employed. F.lectrodes ending in small blunt points (knobs). 



