THE PRODUCTION OF MOVEMENT. 381 



simply reinforces another alreach^ under way, must not be 

 confounded with reflex acts properly so called, in which new 

 activities are originated by the stimulus. All instinctive 

 performances and manifestations of emotion are reflex acts. 

 But underneath those of which we are conscious there seem 

 to go on continually others smaller in amount, which 

 probably in most persons might be called fluctuations of 

 muscular tone, but which in certain neurotic subjects can 

 be demonstrated ocularly. M. Fere figures some of them 

 in the article to which I have already referred.* 



Looking back over all these facts, it is hard to doubt the 

 truth of the law of diffusion, even where verification is be- 

 yond reach. A process set up anyiohere in the centres reverber- 

 ates every ivhere, and in some ivay or other affects the organism 

 throughout , making its activities either greater or less. We 

 are brought again to the assimilation w^hich was expressed 

 on a previous page of the nerve-central mass to a good con- 

 ductor charged with electricity, of which the tension can- 

 not be changed anywhere without changing it ever^^where. 



Herr Schneider has tried to show, by an ingenious and 

 suggestive zoological review,t that all the special movements 

 which highly evolved animals make are differentiated from 

 the two originally simple movements, of contraction and ex- 

 pansion, in which the entire body of simple organisms takes 

 part. The tendency to contract is the source of all the 

 self-protective impulses and reactions which are later de- 

 veloped, including that of flight. The tendency to expand 

 splits up, on the contrary, into the impulses and instincts of 

 an aggressive kind, feeding, fighting, sexual intercourse, etc. 

 Schneider's articles are well worth reading, if only for the 

 careful observations on animals which they embody. I cite 

 them here as a sort of evolutionary reason to add to the 

 mechanical a priori reason why there ought to be the 

 diffusive wave which our a -posteriori instances have shown 

 to exist. 



I will now proceed to a detailed study of the more im- 



* Revue Phil., xxiv. 572 ff. 



fin the Vierteljahrschrift fill- wiss. Philos., iii. 294. 



