626 COMPARATIVE ELECTRO-PHYSIOLOGY 



contraction, that is to say, in stage B, we shall find that the 

 rate of transformation becomes very rapid. 



The second test, by which we may judge of the progress 

 of molecular transformation in the experimental specimen, 

 consists, as we have seen, in the nature of its reply to 

 stimulus. Thus, in the sub-tonic condition, with its tendency 

 to elongation, the responses are abnormal positive. From 

 this they pass gradually, with the progress of molecular 

 transformation, into the normal negative, the intermediate 

 responses being either diphasic or zero. As the process is 

 very rapid after passing the point of transition, the succeeding 

 responses near this point show a staircase increase. 



Or if we do not wish to record the intermediate series, 

 but merely to observe the terminal transformation into 

 negative, or enhanced negative, due to the ascent of the 

 molecular curve above the transitional point, we may apply 

 a rapid series of stimuli, or tetanisation. We may here, 

 according to circumstances, and the point started from, 

 obtain either (i) abnormal positive transformed to normal 

 negative responses ; or (2) diphasic, passing into normal 

 negative ; or (3) feeble, becoming enhanced, negative 

 response. The idea has been put forward, as already said, 

 that tetanisation enhances the responsiveness of the nerve, 

 by some supposed evolution of carbonic acid. That this, 

 however, is erroneous, has been shown by numerous experi- 

 ments already related, and by the fact that even in inorganic 

 substances, under given circumstances, tetanisation enhances 

 response. Nor is it invariably true, in any case, that its effect 

 is always to enhance response. Under certain conditions, 

 it may actually cause depression. The decisive element in 

 the question of its effect lies in that part of the characteristic 

 curve at which it is applied. If this be immediately after 

 the point of transition its result will be an enhancement. 

 Should tetanisation, however, be applied above the maximum 

 or highest point in the curve, its effect will be the diminution 

 of response by fatigue. 



In order clearly to exhibit the fact that continuous 



