CHAP. XVIII.] POWERS OF HIGHER BRUTES. 309 



intellectual sense of Touch becomes more and more called 

 into play, as it is with human beings. 



In Chapter XII. it has been shown that Intelligence 

 or Reason, as- well as Emotion, have their roots in, and 

 cannot be separated from, Sensorial Activity ; and it has 

 also been shown (pp. 187-191) that the sensorial endow- 

 ments and mental attainments, such as they are, of all 

 animals whatsoever tend to be transmitted in a constant 

 and truly marvellous manner to their offspring. 



The question of the number and the excellence of the 

 Sense Endowments of particular kinds of animals is, there- 

 fore, of considerable importance in relation to the degree 

 of their Intelligence. Each practically new addition or 

 greatly developed activity of this kind, in animals whose 

 intelligence is so far developed as to be obvious and 

 indubitable, cannot fail to give additional breadth and 

 strength to their mental operations to say nothing of the 

 new special knowledge, resulting from its exercise, as to 

 the qualities of the outer world of things by which such 

 organisms are surrounded. 



Gradually altering race experiences, if persistent enough, 

 are certain to leave their marks in the form of minute struc- 

 tural modifications of the Nervous System and these, 

 if not actually recognizable in themselves, reveal them- 

 selves by their effects that is, by the manifestation on the 

 part of such animals of new or altered susceptibilities to 

 Impressions from external things or occurrences. It is a 

 familiar fact that disuse blunts the sensorial powers of 

 individual animals, while use and exercise tend to sharpen 

 them. We can easily imagine, therefore, what potent 

 modifiers ' use ' and ' disuse ' may be when they bear respec- 

 tively upon the same Sense Endowments for generation 

 after generation of some particular kind of animal. 



Inasmuch as nothing like a single serial progression is 



