THE ELECTRICAL SPASM OF DEATH 2OI 



metrically positive. This is true when the excitation, due 

 to section made for the purpose of preparation, has subsided. 

 This stimulation, by causing greater excitation of the inner 

 surface, is liable to induce there a temporary negativity. 

 A gradual rise of temperature, as we saw, caused an increased 

 turgidity of the more excitable lower side of the pulvinus 

 of Mimosa, and this increased turgidity was exhibited 

 mechanically by the erection of the leaf. But the electrical 

 sign of increased turgidity is galvanometric positivity. We 

 have also seen that electrical responses occur equally in 

 motile and non-motile tissues. In the petiole of Cucurbita 

 then, on its more excitable inner surface, we obtain, during 

 the gradual rise of temperature, an increasing galvanometric 

 positivity. This is true only, as has been said before, when 

 the rise is continuous, and not marked by fluctuation. For 

 any sudden variation will act as a stimulus, causing galvano- 

 metric negativity of the more excitable inner side. For this 

 reason it is necessary that the rheostatic resistance inter- 

 posed in the lamp-circuit, for the adjustment of the uniform 

 rate of rise of temperature, should be made at the beginning 

 of the experiment, such tissue being very sensitive to this 

 particular stimulatory action. At the commencement of my 

 investigation I experienced much trouble from the erratic 

 movement of the galvanometer spot of light, and the 

 obtaining of a steady electrical curve seemed at that time 

 almost hopeless. Later on, however, I found that these 

 fluctuations were traceable to temperature-variations, unavoid- 

 ably associated with the attempt to regulate the rise of 

 temperature by movement of the rheostatic slide. It is for 

 this reason, then, that the adjustment must be made, once for 

 all, at the beginning. 



Carrying out the experiment in this manner, I obtained, 

 with various anisotropic organs, a sudden inversion of the 

 electric curve at the death-point. This death-point was 

 found, in all vigorous specimens, from which traces of injury 

 had been removed by previous rest, to occur accurately 

 at 59'6 or 60 C. In these electrical curves, the same 



