214 THE PRINCIPLES OF HEREDITY 



and those which have it not is certainly useful. When feel- 

 ings include pleasure or pain, or the promise of them, they 

 give rise to emotions. They then supply particular motives 

 for action. Many sense-impressions are neither pleasurable 

 nor painful ; or at least the pleasure or pain in them is so 

 faint as not to supply efficient motives for action. If I pass 

 along the street, many objects impress my sense of sight, but 

 to most of these impressions I am quite indifferent. For 

 instance, a scrap of paper drifting on the pavement may be 

 seen but not noticed. But some of the things I see awaken 

 interest. They give immediate pleasure or pain, or the 

 promise of one or other in the future. I note them, and, if 

 the emotion they awaken be strong enough, I feel a desire to 

 take action, which may or may not be balanced by opposing 

 desires. If I act or abstain from acting on that desire my 

 will comes into operation. The action, or the inhibition of 

 it, which follows is voluntary. Now all my actions may be 

 divided into those which are initiated by my will and those 

 which are not initiated by it. The latter are reflex actions, 

 the former are not. 1 The same action at different times may 

 be reflex or voluntary. Thus if I cough or wink because, 

 owing to the presence of an irritant, I am obliged to do so, 

 the action is clearly reflex. But if I cough or wink because 

 I wish to do so, the action is just as clearly not reflex, but 

 voluntary. Reflex Action, therefore, may le defined as action 

 which is not initiated by the will. It is involuntary action, 

 which under normal circumstances invariably follows the 

 application of given stimuli. As we see it may or may not 

 be associated with sensation. 



365. It is difficult to imagine that the convulsions of 

 tickling can serve any function useful to the organism that 

 suffers from them. Probably like the tendon reflexes they 

 are mere by-products of evolution. But the function of the 

 vast majority of reflexes is clear. They have been evolved 

 by Natural Selection to provide useful reactions to simple, 

 but important and generally oft-recurring events events of 

 such a nature that the given reflex reaction to any one of 

 them is, for practical purposes, always the right reaction. 

 Obviously all reflexes, for example those associated with the 

 circulatory, the respiratory, and the alimentary systems are 

 inborn and transmissible. None of them are acquired. Since 



1 Instinctive and automatic actions are usually regarded as in- 

 voluntary. According, however, to the definition in the text they 

 are voluntary. This departure from established custom will be 

 justified later. 



