Oti T1IK XKHVOUS SYSTKM AND ITS, fO.XSKKVATH >.\ 



is a simple example: A dog secretes saliva when shown 

 food which he likes. The reaction is what is sometimes 

 called a psycho-reflex. The trial was made many times, 

 and on each occasion a whistle was blown while the food 

 was displayed. At length the blowing of the whistle 

 without the exhibition of the food sufficed to cause sali- 

 vation. 



The acquired capacity of the nervous system to excite 

 the salivary glands in response to a special auditory 

 stimulus was called by the first observer a "conditioned 

 reflex." Such cases afford a striking proof of the plas- 

 ticity of the adjustor mechanism. Yet it may also be said 

 that they afford evidence of its rigidity. In support of 

 this last statement a curious fact is to be mentioned: it 

 was found that when a dog had become so sensiti/ed that 

 he would produce saliva when the whistle was blown, his 

 system remained quite unresponsive to notes a very little 

 sharp or flat as compared with the pitch employed in the 

 course of training. It is reported further that if a chord 

 of three notes was used instead of a single one the 

 sensiti/ed animal would secrete saliva on the produc- 

 tion of either of the simple constituent tones, but more 

 for two sounded together, and most for the complete 

 chord. 



Have we not here something directly related to the 

 mysterious raj>j>i>/i of hypnotism? It seems strange that 

 a human subject can become indifferent to all voices 

 save one and yield abject obedience to that controlling 

 voice. Hut it may be conceived that this is only an 

 elaborate development of the conditioned reflex. When 

 the hypnotic state was induced the nervous sy.-tem be- 

 came attuned to the particular pitch and timbre of the 

 -peaker's tone-. It is said that these are well enough 

 reproduced by the phonograph to make it possible to 

 -ultitute the instrument for the hypnotist. 



Probably we are all possessed of many conditioned 

 reflexes. The reactions may be hard to detect and still 

 harder to trace to their source.- in past experience. Never- 



