30 ROYAL SOCIETY OF CANADA 



The most constant effect of stimulating the cerebral cortex in the 

 pigeon I have found to be movements of the nictitating membrane. In 

 all cases this structure has been drawn down over the eyeball to a greater 

 or less extent, and if the current used be sufficiently strong, the mem- 

 brane may be held over the eyeball for a brief period. 



The effect is greatest on the opposite side, but is not usually confined 

 to that side. 



The eyelids are usually drawn more or less together at the same 

 time, though this effect is much less constant and pronounced than that 

 just noticed. 



The ai-ea of stimulation which produces these effects and those on 

 the pupil is not a very well defined one, but corresponds fairly well with 

 that indicated by Ferrier. I have frequently got more marked move- 

 ments of the nictitating membrane on excitation of a point a little more 

 forward and outward. The same results follow on stimulating the under- 

 lying white matter of the cerebrum. 



I may say, finally, in regard to the pigeon, that it is very important 

 that the bird be properly under the influence of an anaesthetic, as even 

 in birds not wholly under the influence of ether thei-e may be movements 

 of the head on ap]il3dng an electrical current or a stream of water to the 

 bruin. 



The variability in the result as regards the pupil may be dependent 

 in i)art on the degree of anaesthesia and the varying manner in which 

 the nervous mechanism of the eye is affected, and this is, I am inclined 

 to think, a partial explanation of the unsteadiness of the results, though 

 individual differences must also be recognized. For myself I have not 

 been greatly surprised at this variability, considering the nature of the 

 nervous mechanism of the eye, composed as it is of antagonistic elements, 

 which probably vary a good deal functionally in individuals and during 

 ana'sthesia. 



General Conclisions. 



In the dog, cat, rabbit, cavy, rat and mouse, electrical stimulation of 

 the cerebral cortex over definite regions produces i-egularl}' certain move- 

 ments. 



These animals are, however, not on the same pliysiological plane 

 with regard to this subject. 



The dog and the cat are more closely related, and fall into a i)hysio- 

 logical group by themselves ; the rabbit, the cavy, the i-at and the mouse 

 constitute another group. 



There are well defined differences for the cat and the dog. The 

 same applies to the members of the other grou]). 



In the cat and the dog the motor areas are better defined than in 

 the members of the other group. 



