700 



6oo 



500 



too 



SELF-EXCITATION OF THE ELECTRICAL ORGAN. 579 



Self-excitation of the electrical organ. In the excised Malapteru- 

 rus organ it is but seldom that the response to a single stimulus is the 

 single monophasic change indicated by such electrometer excursions as 

 are outlined in Fig. 294. It generally happens that the subsidence of such 

 an effect is succeeded by the development of a second one, this by a 

 third one, and so on. This tendency of the organ to respond to a 

 single excitation by a rhythmical series of changes, although apparently 

 most marked in Malapterurus, appears to be a property of all electrical 

 organs. In the Torpedo it is demonstrable by a sufficiently wide range 

 of rheotome readings, when the galvanometer is used as the recording 

 instrument. In the portion of organ investigated a series of electro- 

 motive changes are now found, occurring one after another at definite 

 intervals, which at 5 C. are y^ sec. (see Fig. 295). A more striking 

 demonstration of the same characteristic is afforded by the photographic 

 records of the capillary electrometer, when connected with the excised 

 Malapterurus organ. A series of from ten to twenty monophasic changes 

 is now seen to be evoked by the single stimulus. In consequence of 

 the slow subsidence of the meniscus, the successive fresh developments 

 are superimposed 

 one upon another, 

 but the rhythm 

 may be made 

 plainer by convert- 

 ing each mono- 

 phasic change into 

 diphasic condenser 

 discharges, through 

 the interposition of 

 the condenser - 

 plates alluded to in 

 the preceding para- 

 graph. Two illus- 

 trations, with the 

 organ at different 

 temperatures, are given in Fig. 296. The extent of this " peripheral organ 

 rhythm " varies with the temperature, the state of excitability of the 

 organ, and the intensity of the individual responses which compose it. 1 



The multiple response is evoked by a single stimulus of either the 

 nerve trunk or the organ strip. This discovery, made by me in 1886, 

 was confirmed by Schonlein, working with the repeating rheotome, who 

 termed the phenomenon, Selbsttetanisintng. The essential factor con- 

 cerned in its production is undoubtedly the passage through the tissue 

 of the intense current due to the response ; this excites the tissue again, 

 and the same effect is repeated. The following facts, among others, 

 prove that the phenomena are due to such auto-excitation. 2 If two strips 

 of Malapterurus organ, A and B, are arranged as in Fig. 297, and the nerve 

 of one, the primary strip, excited by a single stimulus, then the current 

 due to the activity of this primary strip A will traverse the secondary 

 strip B. By placing the secondary strip B the opposite way round to 

 A, it is easy to see whether it responds to the current produced by the 

 functional activity of A, for if B responds, the electrical effect of its 



1 Gotch, loc. tit. ; Gotch and Burch, loc. cit. ; Schonlein, loc. cit. 



2 Gotch and Burch, loc. cit. 



00 



in 



\ 



IV 



002. 



0'05 



0-06 



FIG. 295. 



