PAPERS ON PSYCHOLOGY AND PHYSIOLOGY 133 



behave in a manner entirely different from that of the 

 well-kno^\ii reflexes. 



Sherrington" has pointed out that, in the typical re- 

 flex, there is no such sunnnation of inhibitory effects as 

 v^e have here demonstrated. As a matter of fact, he has 

 demonstrated that when the interval between successive 

 stimulations is small (1,400 sigma or less) one subliminal 

 stimulus may actually show a facilitating effect on a stim- 

 ulus applied a moment later. At any event, the thresh- 

 hold value just above which the scratch-reflex can be 

 elicited remains constant save when toxic fatigue pro- 

 ducts or drugs are present. In the case of nystagmus, 

 however, there is a constantly rising threshhold value 

 even though it has been demonstrated that fatigue pro- 

 ducts are not present. If in chart II the unbroken hori- 



B 



The line AB represents the stimulus limen just above which incre- 

 ments of electrical stimulation will just excite the 'scratch-reflex.' If the 

 increments of stimulus, c,c,c, etc., are given with small intervals, the 

 threshhold value drops from AB to A'B'. It is not known to rise above 

 AB save under fatigue or when certain drugs are administered. Neither 

 does the threshhold value rise above AB if the intervals between the in- 

 crements of stimulus are long. 



zontal line represents the threshhold value just above 

 which so many units of electric shock will give rise to 

 the scratch reflex, then the course of repeated stimula- 

 tions of this reflex may be pictured by the dotted and 

 the broken lines respectively. In a similar way, (Chart 

 III) the course of repeated excitations of the end-organs 

 in the canals can be illustrated. It Avill be seen that in 



1" Sherrington, C. S., The integrative action of the nervous system, 1906, 

 p 37. 



