PHYSIOLOGICAL RHYTHMS. 3<>7 



zoological scale, a bull-dog is irritated, the prediction 

 is more difficult. He may try to escape or he may try 

 something else ; yet whatever he does he will in most 

 cases react shortly after the application of the stimulus. 

 Stimulate a man and there are possible these forms of 

 reaction with endless elaborations and modifications, but 

 there is also a possible exaggeration of the time which 

 may elapse between the application stimulus and the 

 response. The interval may be only so long as is 

 required to deal a blow, or the man may bequeath 

 his response to an insult to his sons and establish a 

 family feud. The capacity for postponing a reaction 

 is the mark of the more highly developed animals, and 

 especially of man. Often when a reaction takes place 

 it seems to have no apparent relation to the stimuli 

 acting at the moment : in one sense it does not have any, 

 while in another it does. For this reason we have 

 among the higher animals that remarkable discon- 

 nection between the stimulus of the moment and the 

 response to it, which gives the appearance of a mutual 

 independence, and has thus given support to the con- 

 ception of automatism in physiology. 



In the last analysis, however, the incoming stimuli 

 appear as the causes of all our actions. The chain of 

 events is often long and hard to follow ; but so much 

 evidence stands on the side of the reflex nature of all 

 actions, that the hypothesis of automatism is not longer 

 necessary. 



The facts which have been reviewed show that in the 

 nervous system there are changes continually going on, 

 changes which are often rhythmic, and which, because 

 they are easily diffused, affect the system as a whole, 

 just as surely as the displacement of any member must 

 affect the motions of a planetary group. Yet it is only 

 here and there, or now and then, that this ceaseless flux 



