1888.] the Electrical Organ of Torpedo marmorata. 419 



heterodromous. The homodromous current must therefore either 

 encounter less resistance than the heterodromous, or its electromotive 

 force must be suddenly strengthened, and that of the heterodromous 

 current weakened, by the sudden establishment in the tissue of a new 

 source of electromotive energy. The first is the view taken by 

 Professor du Bois-Reymond. 



(1.) The present rheotome experiments reveal (a) the new fact 

 that the passage of such intense currents of short duration is always 

 followed by an excitatory response (shock) in the tissue ; (b) that if 

 the intense current due to this response is allowed to affect the gal- 

 vanometer as well as the induced or other exciting current, then by 

 obvious algebraic summation the homodromous deflection must be 

 much larger than the heterodromous ; (c) and that when by means of 

 a fast-moving rheotome the induction shock only is allowed to affect 

 the instrument, no irreciprocity is found. 



The author therefore assumes that the phenomena of irreciprocal 

 conduction are in reality excitatory phenomena, the nature of which, 

 from the methods of investigation used, have not been recognised. 



(2.) The time relations of this response of the isolated strip of the 

 organ to the direct stimulation by the traversing induction shock are 

 now for the first time investigated, by means of the rheotome, and the 

 influence of temperature and other conditions upon these is shown by 

 experimental evidence. 



II. The second part deals with entirely novel phenomena, namely, 

 the excitation of the organ by the current of its own excitatory state. 

 It is shown that in vigorous summer fish every response of the whole 

 or part of the organ to a single excitation of its nerves is followed by 

 a second response, due to the passage through its own substance of 

 the intense current of the first response. In other words the shock 

 of the organ excites its own nerve fibres and nerve endiugs, pro- 

 ducing a feebler second shock, which in a similar manner evolves a 

 feebler third shock ; this a fourth, and so on. 



The response of the isolated organ to nerve excitation is thus 

 multiple ; a primary, secondary, tertiary response following the appli- 

 cation to the nerve of a single stimulus. Since all these responses 

 produce currents similarly directed through the columns of the organ, 

 each column during its activity must reinforce by its echoes the force 

 of the primary explosion, both in its own substance and also in that 

 of its neighbours. 



