DETECTION OF LATENT STIMULUS 



467 



induction-shocks, increasing in arithmetical progression as 3 

 to 5 to 7, were determined. Tetanic shocks of the described 

 intensity — 3, 5, 7 — the total application of each group being 

 a period of 5", were now given, response being taken after 

 each. In this manner two series of responses were obtained at 

 the temperatures of 30 C. and 37 C. At both temperatures 

 with the stimulus-intensity of 3, the 

 responses given by this particular 

 specimen were the same. But while 

 at 37° C. the lower of the two 

 curves, showing the relation between 

 stimulus and response, is a straight 

 line, that at 30 C, the upper of the 

 two, is seen to ascend more steeply 

 and to exhibit convexity to the 

 abscissa (fig. 186). 



After-effect. — The phenomenon 

 which is generally referred to as the 

 after-effect is characterised by so 

 many complexities as to have been 

 regarded as highly perplexing. After 

 the foregoing analysis, however, by 

 which it has been resolved into two 

 elements, much of this obscurity 

 will be found to have disappeared. 

 We saw that the first effect induced 

 by a very strong or long-continued 

 external stimulus consisted in bring- 

 ing about the continuation of the 

 direct effect itself, its persistence 

 depending on the intensity and 

 duration of that stimulation. And 



this we have distinguished as the positive after-effect. A com- 

 ponent part of the external stimulus, however, as we also saw, 

 becomes latent, thus increasing the internal energy ; and the 

 expression due to this element — the negative after-effect — is 

 opposite in sign to the effect of direct stimulus and its positive 



'5— A-f 



Fig. 186. Curve showing 

 the Relation between 

 Stimulus and Response 

 in the same Organ, under 

 the two different Tonic 

 Conditions of 30 C. (upper 

 curve) and 37 C. (lower 

 curve) 



The abscissa represents the 

 intensity of stimulus, and 

 the ordinate the extent of 

 response. The response 

 was the same in both cases 

 when the stimulus-intensity 

 was 3 ; but later, the 

 curve for 30 C. is seen 

 to rise more steeply than 

 that at 37 C, exhibiting 

 at the same time convexity 

 to the abscissa. 



