On the Electric Organ in Malapterurus electricus. 439 



potential difference between two points, 15 mm. apart, in volts ; the 

 abscissae represent time-intervals after the moment when the nerve was 

 excited. 



Comparing these results with those quoted on p. 384 of our previous 

 paper, it will be seen that the initial delay (0*0170 sec. and 0*0180 sec.) 

 is longer than that obtained in our earlier experiments (0*010 sec), 

 and also that the duration of the organ response is longer (0*0390 sec. 

 instead of 0*021 sec), although the temperature was nominally the 

 same, viz., 5° C, in both investigations. It must, however, be noted 

 that in the previous research the organ was simply laid upon a glass 

 stage kept at 5° C. by water flowing beneath it, whereas in the present 

 case the preparation was completely enclosed in a large chamber cooled 

 to 5° C* Undoubtedly the actual temperature of the whole organ 

 strip was higher than 5° C. in our earlier work, and we have ample 

 evidence that in the case of nerve the time-relations of the electrical 

 response are considerably affected by slight changes of temperature at 

 or about 5° C. It should be further noted that the curve now obtained 

 is on a much larger' scale than any of those referred to in our previous 

 research, and in consequence the small beginnings of the rise of E.M.F. 

 can be detected at an earlier stage. The curve is that due to the first, 

 or initial, response of a series produced by self-excitation ; the com- 

 mencement of the second member of the rhythmical series caused by 

 such self-excitation is indicated in the plotted curve (fig. 2), but since 

 the object of the experiment was to determine the development of the 

 initial shock, no attention was paid to the other members composing 

 the organ discharge. 



The following points brought out by the analysis must be dealt with 

 in more detail : — 



(1) There is no trace of any second phase of opposite sign. This 

 characteristic of the organ response is in accord with all previous 

 experiments. It is obviously associated with the circumstance that, 

 since each disc with its nerve endings forms an independent system, no 

 structural basis is furnished for the propagation of the excitatory 

 change from one such system to its neighbours. 



(2) The potential difference between the terminals rises more rapidly 

 than it falls (rise, 0*0070 sec; fall, 0*0160 sec). Since propagation 

 in the organ does not exist, the rate of development and of decline in 

 the potential difference is the nearest approach yet obtained to the time 

 relations of a localised electrical response in an excitable tissue. It is 

 magnified by the circumstance that such local response occurs almost 

 simultaneously in a whole series of nerve endings. We regard the 

 whole analysis as probably typical of the explosive electrical effect 

 which is evoked in nerve endings when these are at 5° C, and are 



* For description of chamber, see Grotcli and Burch, ' Journ. of Physiol.,' vol. 24, 

 1899. 



