CHAPTER XXVII 



SIMILARITIES OF RHYTHMIC RESPONSE IN VEGETABLE 

 AND ANIMAL TISSUES 



The similarities, in their fundamental characteristics, of rhythmic tissues, animal 

 and vegetable : (i) In responses— (2) In possession of long refractory periods - 

 (3) In incapability of tetanus — Theories regarding the causation of heart-beat 

 — The similarities of rhythmic tissues, animal and vegetable, as seen in : ( 1 ) 

 The effects of internal hydrostatic pressure— (2) The effects of variation of tem- 

 perature— (3) The periodic groupings of response— (4) The effect of barium 

 salt— (5) The antagonistic actions of acid and alkali — Identity of rhythmic 

 phenomena in animal and vegetable tissues. 



I HAVE, in the course of the previous chapters, shown the 

 remarkable general similarities, extending through numerous 

 details, between the responses in animal and vegetable tissues. 

 These similarities, however, become still more striking when 

 we compare the special characteristics of those plant and 

 animal tissues which exhibit the property of rhythmicity — that 

 is to say, those tissues which, under the action of a single 

 strong stimulus, give rise to a multiple and rhythmic series of 

 responses, such responses, under favourable circumstances, 

 passing into the so-called automatic movements. 



In animal tissues, such rhythmic movements may be 

 observed in their perfection in the case of cardiac muscle. 

 The isolated heart, when brought to a state of temporary 

 standstill, will give, in answer to a. single stimulus, a single 

 response, or to a sufficiently strong stimulus a multiple series of 

 rhythmic responses ; and under favourable circumstances it 

 will give automatic responses for a considerable length of time. 



Similarly, the plant Biophytum, under exceptionally 

 favourable circumstances, exhibits what are apparently auto- 

 matic responses ; and again, under ordinary conditions it 



