I7O COMPARATIVE ELECTRO-PHYSIOLOGY 



reversal, the living becoming increasingly positive, as com- 

 pared with the dying. An inspection of the curve (fig. 113) 

 shows that while there is a point in the tissue between the 

 dying and the dead, which is equipotential with the living, 

 the completely dead tissue is positive to the living. 



I next carried out an experiment in which death was 

 artificially induced, by immersing a portion of the tissue in 

 boiling water. In connection with this, I may say that it is 

 extremely difficult to ensure the complete death of a thick 

 tissue. It is only the outside layers which undergo death 

 easily, but the interior tissues, from their protected position, 

 are extremely resistant, and it is only after prolonged 

 immersion in boiling water that death can really be ensured 

 throughout. In the present experiment, however, where 

 only a part of the tissue is to be killed, such prolonged 

 immersion would cause death to encroach upon those 

 portions of the tissue which were intended to be kept 

 alive. This difficulty was met by choosing a specimen, 

 the inside of which was accessible to boiling water. The 

 peduncle of the water-lily (Nymphcea alba) in transverse 

 section appears extremely reticulated, and there is thus no 

 difficulty in exposing all its parts to the direct action of the 

 hot water. 



The upper end of the peduncle was kept surrounded by 

 a cloth moistened in ice-cold water, the lower end being 

 immersed in boiling water for ten minutes. The specimen 

 was then placed in tepid water, and allowed to cool down 

 slowly. In this way a length of the peduncle was ob- 

 tained, in which one end was completely killed, whereas 

 the other remained fully alive, the intermediate portions 

 showing all stages of the transition from the living to 

 the dead condition. In order to determine the electrical 

 distribution in its different parts, I now employed the 

 potentiometer method of balance. One electrode was per- 

 manently connected with that dying point which by a 

 previous test had been found to exhibit maximum nega- 

 tivity. The second electrode was placed at successive points, 



