642 COMPARATIVE ELECTRO-PHYSIOLOGY 



commences they had begun to decline. In the series then 

 recorded (fig. 397) we see how the depressed contractile 

 responses are gradually transformed into abnormally expan- 

 sive, through an intermediate diphasic. 



Vic,. 397. Fatigue in Indiarubber giving rise to Diphasic and Reversed 

 Responses 



In the next series of mechanical records, obtained from 

 nerve of frog (fig. 398), we have results exactly similar. The 

 depressed contractile negative here passes through diphasic 

 to abnormal positive. Thus, during the descent of the 

 characteristic curve we obtain, as ha's been said before, a 



FIG. 398. Fatigue inducing Diphasic Variation and Reversal of Normal 

 Response in Frog's Nerve 



a, Diminished normal response ; after tetanisation, enhanced fatigue in- 

 duces diphasic passing into reversed positive response, b ; a period of rest 

 after this revived the normal response in c ; after long-continued tetani- 

 sation, response is seen to be abolished in d, by the death of nerve. 



repetition, but in reverse order, of all the phenomena seen 

 during the molecular ascent ; the sequence of responsive 

 variation was from abnormal positive, through diphasic, to 

 increasing negative. During the descent the sequence is 

 diminishing normal response, diphasic, and abnormal positive. 



