26 BIOLOGY AND SOCIAL PROBLEMS 



though they were without experience and in a 

 way essentially stupid. Memory seems to have 

 vanished from them and with it the basis for 

 intelligent action. The animal responds to 

 stimulation like a nervous machine and with- 

 out reference to past or future. 



What it is that the cortex contains and 

 that molds our responses into intelligent acts 

 is our store of experience. During normal life, 

 as we have already seen, a flood of impulses 

 due to the stimulation of sense organs by ex- 

 ternal changes pours into the central nervous 

 organs ; many of these reach the cortex and 

 some leave on this organ a more or less per- 

 manent impression. These elemental impres- 

 sions are the materials out of which our men- 

 tal life is built. All our thinking is made up 

 of a redistribution and readjustment of these 

 elements. From the highest flights of poetic 

 imagination, from the aspirations of the most 

 devout to the extreme speculations of the 

 philosopher, mathematician, and devotee of 

 science, all are but readjustments and deriva- 

 tions of this mass of incoming material. With- 

 out this spring of supply the human brain 

 would be a barren and arid waste incapable 

 of bringing forth signs of intelligence. The 



