NERVOUS DISCHARGES 17 



3. If the impressions are followed by a period of rest, the 

 longer the rest the greater will be the decrease found in the 

 susceptibility. That is to say the susceptibility of a channel 

 decreases with disuse. 3 



4. There is, however, a permanent increase in the suscepti- 

 bility of a nervous channel caused by repeated discharges. 



5. If a given channel has several sensory endings Si, S2, S3 

 and one or more motor endings M, a discharge from Si to M 

 will increase the susceptibility to a discharge from S2 or S3 

 to M. Hence if Si and S2 are excited in succession there will 

 be a temporary increase in the susceptibility of the channel 

 and also a permanent growth. 4 



6. When several channels are open to a nervous discharge, 

 the discharge . will be divided among the channels in proportion 

 to the susceptibility at the time. 



In order to save space no attempt will here be made to prove 

 the reasonableness of the above premises. It is proper to say, 

 however, that in the main they are in accord with the state- 

 ments of writers of authority as will be found on consulting 

 well known works on the subject. 5 



It may help some thinkers to form a clear idea of the effect 

 of the time interval between discharges upon the susceptibility 

 of the channel if we present it in the shape of a formula: 



Let 



CT = Combined present capacity of all channels 



Ci == Present capacity of the given channel 



CP = Original capacity of the given channel plus 



the permanent increase made by previous 



discharges. 

 CL = Temporary additional capacity of the given 



channel at the last discharge 

 t = Time since the last discharge through the 



given channel 



— ■■- - ■-■-■' 



3 Thorndike, E. L. Animal Intelligence. New York, 1911, pp. 44, 249. 

 Meyer, Max. Fundamental Laws of Human Behavior. Boston, 1911, p. 86. 



4 Meyer, Max. Fundamental Laws of Human Behavior. Boston, 1911, p. 129. 



5 Special reference should here be made to the recently published book of Pro- 

 fessor Meyer, Fundamental Laws of Human Behavior, for the reason that his 

 argument is not altogether unlike that of this article. The writer will not presume 

 to pass judgment on the book further than to say that in spite of its illuminating 

 and most suggestive exposition it leaves room for further elucidation of the matter 

 in hand. 



