THE CEREBRUM 271 



prising when it is admitted that in the substance of this part of 

 the encephalon is the seat of those faculties which manifest 

 themselves in mental operations. 



The seat of the changes, if they be changes, which result in 

 mental operations is supposed to be in the frontal lobes; these 

 are insensible and inexcitable, but severe injury to them, as by 

 hemorrhage, is followed by a cessation of mental activity; con- 

 genital defects also cause a corresponding decrease in the mental 

 caliber. 



From what has been said it is evident that the cerebral hemis- 

 pheres are capable of generating motor impulses and receiving im- 

 pressions general and special; but predominating in importance 

 over these functions is the fact that the gray substance of the 

 cerebrum is essential to the exercise of the intellect even to the 

 existence of that indefinite something called the mind. 



It is by the cerebrum that we perceive and retain impressions, 

 that we understand, imagine, reflect, reason and judge, and thus 

 concoct and issue the mandates of our will. It is the link which 

 connects our impressions and our purposeful actions. 



In animals upon which experiments have been made it is 

 found that life may persist for 'a time after the removal of the 

 hemispheres, and that, outside of the cessation of mental activity, 

 the results are not so marked as one would on first thought sup- 

 pose. Stupor and absence of the ordinary instinctive acts (as 

 corresponding in a way with acts of the will in man) are noted, 

 but voluntary motion and general sensibility are not destroyed, and 

 may be but little interfered with. Of course there is no volun- 

 tary motion in the sense of carrying out the behests of the will, 

 for the organ of the will is destroyed; nor is there any record of 

 painful impressions, for the organ of memory is absent. But the 

 animal can pertorm various consecutive and coordinate move- 

 ments, such as walking, swimming, etc. For example, a pigeon 

 thus mutilated will fly when thrown irtfo the air. This does not 

 argue any mental operation. A person does not ordinarily 



