I 88 MAN, THE ANIMAL 



he does not then it is a bad day. The problem 

 of teaching the racoon was easily compared to 

 this same problem in man because the racoon has 

 but 'two types of learning and two types of for- 

 getting.' " 



The earthworm and frog were stimulated 

 through their receptors for light principally while 

 the racoon was allowed to satisfy its hunger and 

 thus was stimulated indirectly through its intero- 

 receptors. In each of these striking examples of 

 learning, the receptors were employed as the 

 initial avenue of approach. Some natural stimu- 

 lus was selected and one to which the animal 

 would naturally respond. From the discussion in 

 the earlier part of this chapter, it is clear that 

 when such a stimulus started over an appropriate 

 sense organ that its main routes in the nervous 

 system and final destination were pre-determined. 

 This would be true whether the animal was being 

 experimented on by Nature or by Man. 



On the other hand, there is another factor to 

 be reckoned with, for it is very much doubted if 

 a single sensory impulse can alone produce a re- 

 action. The keenest thinkers recognize that ele- 

 mentary reflexes are impossible in any of the 

 higher animals because normal responses in them 

 are dependent upon sensory impulses from vari- 

 ous sources. There is what is termed a summing 



