64 INSTINCTS 



will set a terrier in pursuit : he will growl in his 

 sleep if he dreams of the experience. Memory 

 should, then, be represented in the machine by 

 another set of starting levers, separate from but 

 linked with those that represent sensation. In 

 an animal that possesses memory, sensory im- 

 pressions always arouse recollections, and have 

 thus the effect of releasing not single impulses 

 but assortments of impulses ; and its conduct is, 

 accordingly, not the simple and direct result of 

 sensation, but is determined by the predominance 

 of one impulse, or of a certain mixture of impulses, 

 over a number of competitors. The winning 

 impulse, or assortment of impulses, gains the 

 mastery on some occasions by its intrinsic force- 

 fulness ; on other occasions because it is reinforced 

 by an instinct which was in dominance at the 

 time it was aroused, because its influence has been 

 swollened by habit, 1 because it is endorsed by 

 reason, or because it is selected by the will. 



This view will be rejected by many of the highest 

 authorities. They maintain that each starting- 

 lever or nerve-cell is supplied with a stock of 

 energy of its own ; that it is equipped, so to 

 speak, with a little charge of explosive which is 

 fired when the nerve is touched, and propels the 

 machinery. They maintain, in fact, that the 

 nerves not only start the machinery, but drive it. 

 Indisputably the nerves are furnished with sup- 

 plies of explosives, the replenishment of which is 

 one of the functions of the digestive, respiratory 

 and circulatory systems of the body. The theory, 

 accordingly, gains some corroboration from a 

 scientific fact. And to minds of a materialistic 

 tendency it is more attractive than a hypothesis 

 which postulates the existence of a number of 



1 We shall see, later on, how potent is the effect of habit in con- 

 trolling the conflict between antagonistic impulses. 



