XII. 



THE EXPRESSION OP THE EMOTIONS IN 

 MAN AND OTHER ANIMALS. 



The subject is treated under three Principles : the Prin- 

 ciple of Associated Habit; the Principle of Antithesis ; 

 and the Principle of the direct action of the nervous 

 system independent of Will and Habit. 



THE PEIKCIPLE OF ASSOCIATED HABIT. 



Expression of I* is notorious how powerful is the force 

 the Emotions, of habit. The most complex and difi&cult 

 ^*^* ■ movements can in time be performed without 

 the least effort or consciousness. It is not positiyely 

 known how it comes that habit is so efficient in facilitat- 

 ing complex moTements ; but physiologists admit that 

 " the conducting power of the nervous fibers increases with 

 the frequency of their excitement." This applies to the 

 nerves of motion and sensation, as well as to those con- 

 nected with the act of thinking. That some physical 

 change is produced in the nerve-cells or nerves which are 

 habitually used can hardly be doubted, for otherwise it is 

 impossible to understand how the tendency to certain ac- 

 quired movements is inherited. 



p ^ It is known to every one how difficult or 



° ' even impossible it is, without repeated trials, 



to move the limbs in certain opposed directions which 



