ORGANIC MOVEMENTS 55 



case. Nor is there " action " in the case of so-called 

 muscular " fatigue." 



But both these phenomena, especially functional adapta- 

 tion, that is, an improvement of functioning by functioning 

 itself, may be combined with real acting, and, indeed, there 

 is one group of facts in which this combination is very 

 important. You all know the process which is commonly 

 called the mechanisation of acting ; the piano-player offers 

 a good instance of it, but any one going down a staircase 

 is also an example. Popular psychology says that here 

 we see complicated motions, which, though under the 

 control of consciousness when first learned, are freed from 

 this control later on. It would be more correct to say 

 that one and the same action-effect, repeated very many 

 times, may combine with functional adaptation of some 

 unknown part of the nervous system in such a way as to 

 acquire almost the character of a typical reflex. This 

 process of what is called " exercise " is by no means identical 

 with the process of acting as such, and we have devoted 

 these few words to it in this place in order that we may 

 exclude it from our studies later on. 



Moreover, we are not entitled to speak of an " action," 

 if one and the same stimulus has different motor effects 

 according to the variation of certain physiological conditions 

 which are not concerned in the specificity of anything 

 motorial. Such cases are well known among lower animals, 

 and in dealing with the directive motions and with the 

 recent discoveries of Jennings we have already mentioned 

 a few instances in which changes in temperature or salinity, 

 or in the degree of hunger, also change the sense of response 

 to external stimuli. In such cases there is nothing like 



