SELF-EXCITATION OF THE ELECTRICAL ORGAN. 581 



fore, that the electrical current of an active strip is fully capable of 

 exciting another strip, but it can also excite the nerves of its own 

 plates. This is 

 demonstrated by 

 section of the 

 single nerve 

 which lies upon 

 the under sur- 

 face of a Mala- 

 pterurus strip, so 

 that one end 

 only is left with 

 its nerve fibres 

 in connection 

 with the nerve 

 outside the or- 

 gan, as in Fig. 

 299. On exciting 

 the nerve of the 

 preparation, and 

 connecting suc- 

 cessively the two 

 halves, proximal 

 and distal re- 

 spectively, with 

 the electro - 

 meter, responses 

 are obtained in 

 both, but the 

 record of the 

 distal one differs 

 from that of the 

 proximal in hav- 

 ing an extra 

 period of delay. 



FIG. 298. A, Outline of electrometer excursion obtained from primary 

 strip of Malapterurus organ in response to a single excitation 

 of its nerve. T = 15 C. First response occurs O'OOS sec. after 

 excitation. B, Outline of excursion obtained from a secondary 

 strip, through which current produced by A has been led. The 

 secondary strip, having been arranged the opposite way round, 

 will show, when excited by the current of A, a response of oppo- 

 site direction to that of A. First response 0'03 sec. after excita- 

 tion of A at moment x. The derivations of two of the responses 

 of A are seen in front of the response of B at 0*01 sec. and 

 0'021 sec. respectively. 



Thus, in one instance, the two periods of delay were '01 sec. and '04 sec. 

 respectively. 



The successive responses 

 in Malapterurus follow one 



the ^ 



Division of 



another with 



Tail end 

 of organ- 



utmost 



regularity, the rapidity of 

 the succession being influ- 

 enced by temperature. Thus 

 at 30 C., a rate of succession 

 of 300 per sec. was recorded ; 

 whilst at 5 C. it sank to 100. 

 The state of excitability of 

 the tissue has a great effect 

 upon the production of the 

 phenomenon. A freshly pre- 

 pared organ strip and the 

 organ in the living fish always 

 show the multiple effect, but it is possible by keeping excised strips in 



Llarif 

 'ircuit 1 



FIG. 299. 



