24 ROYAL SOCIETY OF CANADA 



not spontaneous, ure nearly as perfect afterwards as before, and much 

 lii^dit is thrown on the nature of reflexes. 



I have, after careful investigation, been unable to tind any motor 

 •cortical centres whatever. The whole cerebral cortex appears to be 

 absolutely inexcitable, except, perhaps, as concerns certain eye move- 

 ments, and as for these a strong stimulus is required, it is doubtful if 

 they are of cortical origin in the usual sense of the term. 



Nevertheless, unless we deny the existence of voluntary movements 

 to the bird — an extreme position — we are landed in physiological diffi- 

 culties, inasmuch as it has been assumed by nearly all physiologists that 

 the cortex is essential to voluntary movements. The case of the bird 

 seems to me to show that we have much to learn as to the nervous 

 mechanism of voluntary movements, notwithstanding all the investiga- 

 tion that has been given to this subject. 



Conclusions. 



In the dog and the cat there is a period extending from birth to 

 about the time of the opening of the eyes characterized by reflex move- 

 ments, the sway of instincts and the absence of intelligence. During 

 this time the cerebral cortex is inexcitable by electrical stimulation, so 

 that the psychic condition during the blind period is correlated with an 

 undeveloped state of the motor centres of the cortex of the cerebrum. 

 The advance in movements, first of the limbs and later of the head and 

 face parts, together with the psychic progress associated with this is 

 ■correlated with the rapid development of the cortical centres for the 

 limbs in the first instance, and later for the head and face in the period 

 immediately following the blind stage. 



. This is more rapid and more pronounced in the cat than in the dog, 

 and is coi'related with the greater control in the cat over the fore-limbs 

 and with certain physiological and psychic developments characteristic 

 of the cat, 



Siniilar conclusions apply to the rabbit. exce})t ihal the difference in 

 the rapidity of development of head and face movements is correlated 

 with an earlier oi'ganization of the corresponding cortical centres, and 

 that there is a greater difference between the fore-limb and the hind- 

 limb, with all of which there are special psychic correlations bound up 

 with certain peculiarities of the rabbit's modes of life. 



The vast difference in physiological and psj'chic development of the 

 t-av}' at birth is correlated with the presence of cortical cerebral centres 

 readily excited by artificial stimuli, centres Avbich in a few days reach a 

 practically perfect state of development. 



The psychic manifestations of the ))igeon and the fowl have not the 

 asame sort of cerebral cortical correlates as the animals referred to above. 



