n8 Instinct and Intelligence 



tive actions are retained. If an obstacle is 

 placed in the path of an animal which has been 

 thus mutilated, and it is then excited by a prick 

 in its foot, it moves away so as to avoid the 

 obstacle. The mere act of leaping away may 

 possibly, in case of necessity, be regarded as a 

 reflex action; but the fact that the frog avoids 

 the obstacle shows that its instinctive elements 

 are still at work, and are located in the nervous 

 substance of the basal ganglia. 1 



Reptiles form the lowest class of vertebrates 

 which lead a wholly terrestrial existence, their 

 lives depending on the perfection of their 

 visual, auditory, and tactile sensory organs and 

 the corresponding cerebral centres. The living 

 substance of these organs has, among the 

 " fittest " of this class of beings, responded to 

 the streams of energy derived from new and 

 varied external sources. For instance, the eyes 

 of reptiles have developed structures whereby 

 they 'focus on their retina waves of light pro- 

 ceeding from near and distant objects. Their 



1 Professor Schrader concludes from the result of his experiments 

 on frogs, that their central nervous system can be divided into a 

 series of sections, each of which is capable of performing an 

 independent function. 



