CHAPTER XLII 



MODIFICATION OF RESPONSE UNDER CYCLIC 

 MOLECULAR VARIATION 



Anomalies of response Explicable only from consideration of antecedent 

 molecular changes Continuous transformation from sub- tonic to hyper-tonic 

 conditions Two methods of inquiry, first by means of characteristic curves, 

 second by progressive change of response Abnormal response characteristic 

 generally of A or sub-tonic state Abnormal transformed into normal, after 

 transitional B state B state characterised by staircase response Responses at 

 c stage normal and uniform At stages D and E responses undergo diminution 

 and reversal Responsive peculiarities seen during ascent of curve, repeated 

 in reverse order during descent All these peculiarities seen not only in living 

 but also in inorganic substances, under different methods of observation 

 Elucidation of effect of drugs Response modified by tonic condition and past 

 history. 



WE have seen that, normally, the phenomenon of response 

 in living tissues is very definite. There are other con- 

 ditions, however, under which it is found to be modified or 

 even reversed. These abnormal effects may be brought 

 about, either by feeble stimulation, or by changes in the 

 responding tissue itself. Thus, though moderate stimulus 

 evokes normal negative response, a feeble stimulus will often 

 be seen to induce the abnormal positive, and this is most 

 easily observed in certain particular modifications of the 

 tissue associated with sub-tonicity. The fatigue-changes 

 due to excess of stimulation are also, curiously enough, 

 effective in bringing about the same abnormalities of response. 

 It is open to us to regard these anomalies as the result of 

 obscure vital actions, and therefore incapable of further 

 analysis. Or, since the phenomenon of response itself is 

 admitted to be due to the molecular upset caused by 

 stimulus, their origin may be looked for in the antecedent 



