VARIOUS TYPES OF RESPONSE 



conspicuous by the summation of the after-effects of all the 

 preceding stimuli with the direct effects of their successors. 

 The staircase effect is seen in the two accompanying records. 

 In fig. 55 is given a photographic record of the staircase 

 increase in the electrical response of a vegetable nerve l in 

 somewhat sub-tonic condition. In fig. 56 we have a second 

 example of this effect, seen in the electrical response of the 

 petiole of Bryophyllum, rendered artificially sub-tonic by 

 cooling. 



We next arrive at the C stage, which is, as has. been said, 

 one of more or less stability. Expenditure is here, for a 



certain length of time, balanced by 

 income. The molecular condition 

 of the tissue being thus constant, 

 the responses are uniform. I give 

 below records of such uniform re- 

 sponses to uniform stimuli, ex- 



FIG. 55. Photographic Re- 

 cord of Staircase Response 

 in Vegetable Nerve 



Fig. 56. Staircase Increase 

 in Electrical Response of 

 Petiole of Bryophylhtm, 

 rendered sluggish by 

 cooling 



hibited by different tissues. In fig. 57 are seen uniform 

 electrical responses to uniform mechanical stimuli, given 

 by the root of radish. Fig. 58 shows uniform electrical 

 responses to uniform thermal stimuli, given by the petiole 

 of fern. 



The C is succeeded by stages D and E, representing 

 a condition of over-strain. In fig. 59, a, are shown uni- 

 form responses to uniform stimuli, applied at intervals 



1 An account of the discovery of certain vegetable tissues, wjth the function o.f 

 nerves, will be found in Chapter XXXII, 



