



u 







VARIOUS TYPES OF RESPONSE 89 



electrolyte, surcharged with by-products, so after sustained 

 activity of a living tissue, the process of renewal, or renova- 

 tion, will be necessary. It is thus seen how upon the funda- 

 mental molecular derangement, a chain of very various 

 chemical events may follow, as its after-effect. And it is 

 only by going in this way to the very root of the pheno- 

 menon that we can avoid the many contradictions with 

 which we are confronted by the chemical theory. 



In studying various response phenomena, our conclusions 

 are necessarily based upon the observation of the amplitude 

 of responses. It is therefore important at this point to draw 

 attention to the danger of hasty inferences. On finding, for 

 instance, that the amplitude of response in a given case is 

 diminished, we are apt to infer that the responding tissue 

 has undergone depreciation. But this is not invariably the 

 case. In the entire process of response, while stimulus 

 induces molecular upset, we must remember that there is 

 also an internal factor, which brings about molecular restitu- 

 tion. Now, if this force of restitution be in any way enhanced, 

 it is easy to see that the responsive distortion of the mole- 

 cules will find itself opposed, with consequent diminution of 



mplitude. We shall thus often find that a rise of tem- 

 perature, by enhancing the force of recovery, actually causes 

 a diminution of response. That this is not due, however, to 

 any depreciation of the tissue is seen from the fact that the 

 same rise of temperature enhances another excitatory pro- 

 perty of the tissue -namely, the speed of its conduction. 



I shall now give a brief account of the modifying influence 

 exercised on response by the molecular condition. It will be 

 shown, in the Chapter (XL 1 1) on the Modification of Response 

 under Cyclic Molecular Variation, that a given response is 



ot determined merely by the nature of the responding 

 substance, but also by the amount of the energy which it 

 possesses. Starting from the lowest condition of sub-tonicity, 

 a substance undergoes progressive molecular transformation 

 by the action of the impinging stimulus itself. Five stages 

 may be roughly distinguished in this transformation. In the 



