578 WILL AND 



or fly with as mach vigour and precision as before. In the rabbit 

 the removal of the hemispheres, while decidedly impairing the 

 motility of the fore limbs, does not quite destroy the power of 

 station, or of co-ordinated progression in answer to external stimuli. 



In the dog, however, the removal of the hemispheres 



exercises a much more marked influence on these powers, rendering 

 station and locomotion absolutely impossible" (p. 207). 



(2.) " In proportion, however, as movements at first requiring voli- 

 tional education tend to become organized or rendered automatic, 

 the less are they afl'ected by injury to the cortical centres. Hence 

 in the dog, in which the acquisition of the control of the limbs is 

 speedy, the destruction of the cortical centres produces a much less 

 marked effect; the movements having become in a great measure 

 independent of these, through organization in the subordinate 

 centres " (p. 213). " In the optic thalamus and the corpus stria- 

 tum the association bfttween certain impressions and certain 

 actions becomes so mechanical or organized that if we were to 

 remove from the dog all the centres above the basal ganglia, these 

 would of themselves, on the application of external stimuli, be 

 sufiicient to carry out all the co-ordinated movements of locomo- 

 tion" (p. 214). 



(3.) "The more the control of the limbs depends in the first 

 instance, and continues to be dependent on voluntary acquisition, 

 the more does destruction of the cortical motor centres cause 

 paralysis of movement. Hence in man and the monkey, in whom 

 volition is predominant and automaticity plays only a subordinate 

 part in the motor activities, destruction of the motor centres of the 

 cortex causes paralysis of a very marked character " (p. 213). 



The facts cited in paragraph (1) are important, unques- 

 tionably true, and in part well known. They merely tend 

 to show, that in higher forms of life the Cerebral Hemi- 

 spheres with the Corpora Striata gradually take on some 

 of the functions which in lower animals have been dis- 

 charged through the intermediation of Medullary and 

 Spinal Centres. The Cerebral Hemispheres in higher 

 animals come to exercise, therefore, a larger proportionate 

 share of influence in the execution even of the common 

 movements needed for Locomotion. 



