DIRECTIVE INSTINCT 95 



sympathy must also guide the internal organs of 

 our bodies : the heart and the lungs act with full 

 appreciation of each other's requirements, and the 

 stomach realizes what substances should be 

 accepted, and what rejected by it. But this 

 description is not sufficiently comprehensive. 

 Directive instinct is apparently the energy by 

 which living creatures grow from their initial to 

 their adult stages, and it must therefore include a 

 realization of purposes not merely of the ends to 

 which certain organisms and substances of the 

 environment should be applied, but of the final 

 development to which growth tends. And it must 

 also include a precise and detailed realization of 

 the means by which growth, nourishment, and 

 reproduction are effected. The characteristics of 

 this faculty have already been described. They 

 include independance of experience, inevitability 

 of sequence, and accuracy of execution. An 

 organism that is guided by it knows no doubt or 

 hesitation : it proceeds towards its aim with the 

 unfailing punctuality of clockwork. So appears 

 to us the undeviating regularity of a beehive, and 

 so would appear to us the working of our internal 

 organs could we realize its accurate complexity. 



An accomplishment which simulates the pro- 

 cesses of directive instinct is that known as the 

 " ideo-motor," by which we are able to execute 

 elaborate series of movements, such as those of 

 walking, speaking, or playing the piano, without 

 any dependance upon the brain, each sensory 

 impression or recollection producing the appro- 

 priate muscular reaction by the independent 

 functioning of local nerve centres. But this 

 accomplishment is only acquired by deliberate 

 practice. Processes that are directed by instinct 

 need no practice whatever. A young caterpillar 

 on emerging from the egg is as efficient in its 



