638 COMPARATIVE ELECTRO-PHYSIOLOGY 



relaxation. The only difference lies in the fact that fatigue 

 makes its appearance in the one case earlier than in the other. 

 When dealing with the subject of the enhancement of 

 response by tetanisation, I stated that here it was not 

 tetanisation, as such, which formed the determining factor in 

 bringing about the increase of response ; this was rather due 

 to a phasic molecular transformation, induced by tetanisation. 

 If the substance happen to be in the transitional B phase, 

 then and then only will tetanisation enhance its response. 

 If, however, it should happen to be in the optimum C phase, 

 then the same tetanisation will have the effect of carrying 

 it into D and E, the phases of fatigue. The response here, 



FIG. 395. Photographic Record of Response of Tungsten showing 

 Enhancement of Response after moderate Tetanisation, and Reversal 

 of Response, due to Fatigue under stronger Tetanisation 



instead of being enhanced, will be decreased or reversed. 

 This is seen in the following record (fig. 395) obtained with 

 tungsten when moderate tetanisation enhances response, 

 whereas strong tetanisation, by bringing on fatigue, reverses 

 the normal response. 



How universal are these phenomena will be seen from 

 the accompanying series of records, obtained not only with 

 various living tissues, but also with inorganic substances 

 under parallel conditions, the normal responses being in all 

 these cases reversed by tetanisation, in consequence of the 

 transformation from the C to the E phase. In fig. 396 (a) 

 is seen the normal contractile response of a frog's nerve 

 reversed to the positive or expansional, after tetanisation. 



