THE HISTORY OF MENTAL DEVELOPMENT 145 



begins to show fear, we may feel tolerably certain that 

 it has been conscious of past experience of danger and 

 remembers these experiences. But the sense-organs 

 are all the time improving, whether as servants of con- 

 scious perception or of reflex action, and the develop- 

 ment of the higher sense-organs, especially of the 

 eyes, has called forth a higher development of the 

 brain. The brain continually develops both through 

 constant exercise and through natural selection. 

 Through the higher and more delicate sense-organs it 

 perceives a continually wider range of more subtile 

 elements in its environment. And the higher the 

 sense-organ the more directly and purely does it min- 

 ister to consciousness. The eye, when capable of 

 forming an image, is almost never concerned in a 

 purely reflex action. 



From the constant recurrence of perceptions and ex- 

 periences in a constant order the animal begins to 

 associate these, and when he has perceived the one to 

 expect the other. Out of this grows, in time, inference 

 and understanding. The mind is beginning to turn 

 its attention not merely to objects and qualities, but to 

 perceive relations. And thus it has taken the first 

 step toward the perception of abstract truth. And if 

 it has the aesthetic perception and can perceive 

 beauty, we have every reason to believe that the 

 same faculty will one day perceive truth and right. 

 But on the purely animal plane of existence these 

 powers could be of but little service, and we can ex- 

 pect to find them developed only very slightly and 

 under peculiar surroundings. And in this connection 

 it is interesting to notice the great results of man's 

 training and education in the dog. For the wolf and 

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