CYCLIC MOLECULAR VARIATION 625 



We shall now proceed to the description of the distinctive 

 characteristics of certain molecular states. We may take 

 first the case of nerve, which gives different characteristic 

 responses under different conditions ; and here, employing 

 the simplest mode of record namely, the mechanical we 

 find, as already said, that, when it is cut off from all sources 

 of energy, the specimen is apt to fall into a condition of 

 growing sub-tonicity. This is indicated in the mechanical 



FIG. 382. Mechanical Response of Frog's Nerve to successive equal 

 Stimuli, applied at Intervals of One Minute 



The sloping line at the beginning shows growing elongation due to sub- 

 tonicity. Stimulus here causes positive response. Fourth, fifth, and 

 sixth responses are distinctly diphasic. Responses become normal 

 and increasingly negative after the seventh, with marked staircase 

 increases. Molecular transformation is seen to be very rapid, above the 

 B point of transition. Record is a photographic reduction, half original 

 size, of tracings obtained on smoked glass. 



record by an increasing abnormal elongation, as in fig. 382, 

 given above. When the nerve is now subjected to the 

 action of stimulus, its tonic condition is gradually restored, 

 progressing towards a normal excitatory condition. The 

 molecular transformation involved here is at first expressed 

 by growing retardation of the abnormal elongation, and 

 afterwards by gradual contraction. At the point of trans- 

 ition from positive to negative, or from elongation to 



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