ANIMAL KLECTRICITV. --LECTURE IIL 67 



remote possibility, suogested indeed by one or two 

 peculiar features in the behaviour of isolated nerve, 

 that CO2 evolved in the process of disintegration may 

 conceivably be reinvolved in a process of reintegra- 

 tion ; that, in short, baseless as the idea may seem at 

 present, there may be in an animal tissue an assimila- 

 tion of CO2 analogous with the assimilation of CO^ 

 taking place in vegetable protoplasm. We have rea- 

 son to associate the negative effect with a dissimilatory 

 evolution of CO^, we may some day find reason to 

 associate the positive after-effect with an assimilatory 

 reinvolution of CO^. But at present this is a mere 

 fiying conjecture for which I have no positive base. 



Putting this conjecture aside, let us turn to another 

 less imaginary, yet still distinctly conjectural point. 



Contractile tissue — that of the heart in particular, 

 but also the contractile tissue of jelly-fish, as well as 

 voluntary muscular tissue — exhibits a peculiarity 

 known to physiologists as the "staircase phenome- 

 non." Stimulated at regular intervals, not too long nor 

 too short, by strong induction shocks, such contrac- 

 tile tissue gives a series of responses, each of which 

 is the greatest effort of which the muscle is capable at 

 the time, but each of which is a little orreater than its 

 predecessor. Such an increasing series is called a 

 staircase, and we have seen that a series of electrica 

 responses of nerve exhibits a similar staircase — in- 

 creasing in the case of a series of negative effects, 

 decreasing in the case of a series of positive effects or 



