iMiLLsJ CORTICAL CEREBRAL LOCALIZATION 29 



weak stimulation in the rabbit at all events as the corresponding ones in 

 the dog and eat, if not more so. These are the very movements that are 

 most frequently called into exercise by the life habits of the animals, and 

 it seems to me important to recognize that all cortical centres are not 

 equally well organized, as might be inferred from reading the accounts of 

 some authors on this subject. This applies to the whole question of 

 cortical localization and not to that of the rabbit alone, though, as I have 

 shown, it is specially well illustrated in this animal. 



In my attempts to carry the investigation of cortical cerebral locali- 

 zation downwards in the animal scale I naturally reached the bird. 

 Upon turning to Ferrier's account ' I found that he claimed that stimu- 

 lation of an area in the upper parietal region caused "intense contrac- 

 tion of the opposite pupil, occasionally associated with turning of the 

 head to the opposite side." He further says : •' In a few cases I have 

 also observed, from stimulation of the region below this, turning of the 

 head to the opposite side without contraction of the pupil. Beyond 

 these effects the results of stimulation were entirely negative." 



1 have made a thorough examination of this subject in the pigeon, 

 and have investigated the case of the fowl sufficiently to convince me 

 that there is no dttterence, at all events so far as the main results are 

 concerned. 



The methods employed were the same as for other animals, and the 

 results ma}' be stated briefiy as follows : 



Everj' part of the cortex is refractory to stimulation, so far as move- 

 ments of the neck, head i^arts and limbs are concerned. This also applies 

 to the white matter lying beneath the cortex. 



Stimulation of the cortex may give rise to contraction or to dilatation 

 of the pupil, or produce little or no change in it in either eye. When a 

 change occurs, it is usually greatest on the opposite side, and may be 

 practically contined to that side. 



The result may be momentary or last for an appreciable time — may 

 be a steady effect or oscillatory. Veiy rarely, if ever, can it be main- 

 tained for any considerable period. 



As to whether contraction results or not seems to depend, to some 

 extent, on the condition of the pupil at the time ; for the result has been 

 more frequent when the pupil has been alread}' moderately dilated. 

 Contraction has been more frequent than any other effect. I have not 

 been able to demonsti'ate the conditions under which dilatation takes 

 place, nor the one effect now, and the other again, as sometimes oc- 

 curs. Both dilatation and contraction may occur during experiments 

 made on the same bird. Apparently the conditions are complex and 

 variable. 



' " The Functions of the Brain," 2nd Ed. London, 1886. 



