EFFECT OF TEMPERATURE ON ELECTRICAL RESPONSE 187 



rising temperature. Thus in a certain specimen of Bio- 

 phytmn^ for example, while the velocity of transmission 

 at 30 C. was 37 mm. per second, it became enhanced to 

 9*1 mm. that is, nearly three times when the temperature 

 was raised to 37 C. From these considerations, it would 

 appear that the diminution in amplitude of electrical response, 

 under a rising temperature below the rigor-point, might not 

 always be due to a diminution of excitability, but to some 

 other cause. 



In connection with this, it must be borne in mind that 

 two factors are included in the process of response : namely, 

 the external stimulus which induces contraction, or galvano- 

 metric negativity, and the internal factor which brings about 

 recovery. For I have already shown that whereas the action 

 of stimulus induces one effect the contraction, for example, of 

 an excited tissue with galvanometric negativity an increase 

 of internal energy causes exactly the opposite that is to say 

 the expansion of the tissue and galvanometric positivity. 

 External stimulus and internal energy thus act antagonisti- 

 cally. A steady rise of temperature causes, as we have seen, 

 an increase of internal energy. Hence, increased energy 

 due to rise of temperature, enhancing the force of recovery, 

 may cause a diminution of response, which is not due to 

 diminution of excitability. 



The inference that it is the increased internal energy due 

 to rise of temperature which, by augmenting the force of 

 recovery, diminishes the amplitude of response, appears the 

 more probable from certain characteristics observed in the 

 autonomous pulsation of Desmodium gyrans. If rise of 

 temperature increased the force of recovery, we should 

 expect, conversely, that a fall of a few degrees would have 

 the effect of diminishing this force of recovery, and con 

 sequently enhancing the response. That this actually occurs 

 will be seen in fig. 126, in the first part of which is given 

 a series of responses at the temperature of the room, which 

 was 29 C. When the temperature of the plant-chamber 

 was now lowered to 25 C., the force of recovery would appear 



