CYCLIC MOLECULAR VARIATION 



627 



molecular transformation shows itself in two different ways 

 by a progressive physical change of the substance itself as 

 exhibited by the characteristic curve, and also by a pro- 

 gressive variation in the character of the responses I shall 

 here give a pair of records of the mechanical response of 

 frog's nerve. In fig. 382 the continuous molecular trans- 

 formation caused by impinging stimulus is shown by the 

 growing contraction, or responsive mechanical negativity of 

 the nerve, as seen in the 

 shifting of the base-line 

 upwards. It is also in- 

 teresting to notice here 

 the continuous trans- 

 formation of the in- 

 dividual responses from 

 the abnormal positive 

 through diphasic to the 

 normal negative. There 

 is also the noticeable 

 additional fact that after 

 the point of transition 



is passed the response FlG . 383 . Mechanical Response of Frog's 



Nerve, showing Conversion of Abnormal 

 Positive into Normal Negative Response 



after Tetanisation 



Note also the shifting of the base-line up- 

 wards, and that the individual period of 

 positive is shorter than that of negative 

 responses. 



undergoes a marked 

 staircase increase. In 

 fig. 383 is given another 

 record, obtained with 

 frog's nerve, where, after 

 an intervening period of 



tetanisation, the abnormal positive response is converted into 

 normal negative with staircase increase. The shifting of the 

 base-line upwards is also very noticeable here. Effects pre- 

 cisely similar are observed in the mechanical response of 

 vegetal nerve. 



If we now turn to a different mode of observationsay 

 that by the electro-motive variation the records will be 

 found to bear a remarkable resemblance, in every particular, 

 to those which have just been given. We find here the same 



S S 2 



