GENERAL PHYSIOLOGY OF THE CEREBRUM. 



179 



psychical and motor responses of a much more intricate and in- 

 direct character. 



Extirpation of the Cerebrum. One of the methods used in 

 physiology to determine the general functional value of the cerebral 

 hemispheres has been to remove them completely, by surgical 

 operation, and to study the effect upon the psychical responses of 

 the animal. Upon the cold-blooded animals and the birds the 

 operation may be performed with ease, but in these animals the 

 positive results are not striking and the experiments are valuable 



* J 



4W 



Fi. /9. Sections through corresponding parts of the cortex in: a, Man; ft, dog; 

 and c, mole, to show the greater separation of the nerve cells in the higher animals. 

 (Bethe, after Nissl.) 



chiefly for their negative results. If the cerebral hemispheres are 

 removed from the frog, for example, the animal after recovering 

 from the immediate effects of the operation that is, the effects 

 of the anesthetic and the shock shows surprisingly little difference 

 from the normal animal. It maintains a normal posture and shows 

 no loss at all in its power of equilibration. When placed on its 

 back it quickly regains its usual position. If thrown into water 



