234 IRRITABILITY 



excitation takes place. Here is the key to the understanding of 

 the great variety of interference effects. By determination of 

 these various factors in a given case and their sequence, we can 

 anticipate the nature of the interference which will follow. The 

 complex actions brought about by the various factors, which we 

 cannot at first clearly understand, can be at once interpreted as 

 soon as we convert them into their elements. 



