THE CEREBRUM 273 



It would seem that the cerebrum is a kind of storehouse 

 in which are kept all the materials necessary for the per- 

 formance of all kinds of pro-determined acts, whether they 

 manifest themselves in speech, or thought, or muscular 

 action. What excites these materials to activity i. e., what 

 excites a voluntary act is not clear. We know certain 

 things will usually excite a certain train of thought, or cause 

 us to will to do or say certain things. Such phenomena* are 

 akin to, if not identical with, reflex action. These manifes- 

 tations of our voluntary power are due to impressions con- 

 veyed by afferent fibers to the cortex ; indeed it may be that 

 every afferent fiber in the system exerts an influence thus 

 indirectly upon the organ of the will, "and the impressions 

 conveyed by them are reflected in one's character and life. 

 But it cannot be said that all voluntary activity is thus of a 

 reflected nature; there is some cause other than the recep- 

 tion of afferent impressions which sets the will in operation. 



Connection Between the Brain and Intelligence. It is 

 claimed that a single hemisphere is capable of performing all 

 the ordinary intellectual acts as well as both; and atrophy, 

 or destruction otherwise, of one hemisphere has frequently 

 been noticed to entail no mental defect. But whether the 

 mind under such conditions would be equal to the highest 

 intellectual attainments is doubtful. It would seem that in 

 health the brain unites the impressions received by the two 

 sides (as e. g., through the optic nerves), and the resulting 

 idea is a single one; that is to say a person does not have 

 two opposing ideas about the same thing the same time ; the 

 two hemispheres seem to agree. 



In a general way, it may be stated that the degree of in- 

 telligence corresponds to the weight of the brain, though 

 to this rule there are many exceptions. It may be more prop- 

 erly said that the development of the intellectual faculties is 

 greater as the area of gray matter is increased by the convo- 

 lutions of the cortex. Idiots' brains are usually, though not 

 by any means invariably, much below the average weight. 



