442 



Messrs. F. Gotch and G. J. Burch. 



It must be self-evident to anyone who makes the experiment that 

 the phenomena resulting from the passage of the organ shock through 

 the human body are such as cannot be produced by interrupted battery 

 currents unless the potential is high. It is a matter of common know- 

 ledge that the shock from a healthy fish will pass through a chain of 

 several people holding hands, and will be felt by each, not only in the 

 arms, but in the muscles of the chest and shoulders. No battery 

 current of 30 or 40 volts through such a circuit will do this, however 

 interrupted, unless the circuit has considerable self-induction, in which 

 case the E.M.F. of the battery does not represent the E.M.F. of the 

 shock, which may greatly exceed it. 



It is, therefore, surprising tliat D'Arsonval's investigations led him 

 to give 17 volts, and that Schdnlein gives 31 volts as the maximum 

 E.M.F. of a Torpedo shock. Such low numbers indicate, we think, 

 that the methods used by these observers were not applicable to 

 the measurement of the maximum E.M.F. of the shock of an 

 electrical organ.* This opinion was stated definitely in our paper, 

 and we here repeat the statement because the photographs now pub- 

 lished show plainly that the development of the E.M.F. of an organ 

 shock is, at low temperatures, comparatively slow, much less rapid in 

 fact than that of a battery current thrown in by breaking a short 

 circuit. So far, therefore, as suddenness of change is concerned, the 

 electrical organ is, under these conditions, at a disadvantage as com- 

 pared with a battery current ; yet it can produce muscular contractions 

 such as can only be caused by interrupted currents of high potential. 

 We are, therefore, constrained to believe that the maximum E.M.F., 

 even in Torpedo, will be found to be nearer 200 than 30 volts. At 

 any rate the analysis of the foregoing curves indicates that this 

 maximum, namely, 200 volts, is attained by the organ shock of Malap- 

 terurus electricus. 



The Electrical Resistance of the Electrical Organ. 



Owing to the failure of the organ to respond to further excitation, 

 it was impossible to carry oat the other experiments which we had 

 contemplated. We therefore decided to make such measurements of 

 the electrical resistance of the tissue as could be effected with the 

 apparatus at hand. In the absence of a Kohlrausch bridge we em- 

 ployed a resistance-box of the Post Office type, and used the capillary 

 electrometer as an indicator. With this instrument it is advantage- 

 ous to have the bridge arms of the highest available resistance — in 

 this case 1000 ohms : 100 ohms — as the current is thereby reduced, 

 while the excursions are in no way lessened. For a similar reason a 

 shunt is not employed, but the current is derived from a rheocorcl 



* D'Arsonval, ' Comptes Eendus/ vol. 121, p. 145, 1895 ; Sclionlein, ' Zeitscli. f . 

 Biol.,' vol. 31, N. 13. 



