68 INSTINCTS 



beat time. A lover's thoughts are moved by 

 the sight of his mistress, or by the recollections 

 that are awakened by a letter from her. In some 

 cases an impression arouses a single appropriate 

 impulse : a loud, unexpected sound will always 

 make us start the first step of a movement to 

 escape. But, generally, sensory impressions or 

 recollections have the effect, as it were, of starting 

 a complicated arrangement of machinery, in 

 which a number of impulses are set free to act in 

 combination or in opposition. The result will 

 depend very largely upon habit, or upon the mood 

 we are in at the time, that is to say, upon the 

 effect that has been produced by preceding im- 

 pulses. The crying of an infant may at one time 

 move us to pity, at another time to anger. So the 

 sight of a friend may, on different occasions, evoke 

 feelings of kindness or of impatience. 



Impulses are also released by the tendency to 

 imitate. A chicken is led to peck by the sight of 

 its mother pecking : it may be stimulated by 

 tapping with the finger, or a pencil. Noise impels 

 a canary to sing its loudest ; dogs bark when they 

 hear other dogs. The cruel feelings which are 

 gratified by a bull-fight may be evoked by the 

 excitement of the surrounding spectators. We are 

 stirred by fashion to change the manner of our dress. 

 Self-control is most strongly inculcated by example 

 by a practical stimulus, that is to say, to our 

 imitative faculty. 



We have compared instinctive impulses to 

 main-springs that are released by the touching of 

 a catch. In some cases they are set to a time, 

 like an alarum- clock, and are released automati- 

 cally on the expiry of the period. The growth of 

 an individual, from its first embryonic stage to 

 maturity, is controlled by a number of impulses 

 that act at definite periods and in a definite order. 



