320 



NATURE 



\jFeb, 6, 1879 



THE ELECTRICITY OF THE TORPEDO ' 



II. 



4, /CURRENTS induced by a torpedo discharge are all 

 ^ produced at the beginning of each wave. There are 

 currents induced on the completion of a circuit, i.e., the 

 inverse of the inducting currents, as is shown by the elec- 

 trometer. 



Fig. 7 will show the arrangement of the experiment to 

 prove that the torpedo's discharge in the inductive coil 



Fig. 7. 



(d) produces, in the secondary coil (c) currents of suffi- 

 cient energy to cause movement in the second signal 

 placed in the circuit of the inducted coil. It must be 

 remarked, however, that the electric apparatus which 

 furnishes the indications of the passage of the discharge 

 is not, as shown in the diagram, that which produces the 

 inducted currents. Currents of sufficient intensity would 

 not have been obtained to act upon the electro-magnetic 

 signal, if we had opposed to the passage of the discharge 



a resistance so considerable as that of the coils of the 

 electro-magnet. The difficulty has been averted by using 

 the opposing apparatus for signalling; and this we are 

 authorised in doing, since the discharges are absolutely 

 symmetrical to the right and left when the nervous 

 centres are excited by the magnet. 



That exception made, let us examine the results of the 

 experiment. The traces were placed one over another ; 

 one (as i in Fig. 8) indicating the successive waves of the 

 discharge, and the other (as 2 in Fig. 8) the currents in- 

 ducted by the waves. This figure already shows 

 an important fact : that the number of inducted 

 currents is equal to that of the inducting waves ; 

 and that each inducted current is produced at the 

 commencement of each wave, just as in a galvanic 

 current an inducted current is produced at each 

 completion. But here we only find currents in- 

 ducted by the completion or, more exactly, at 

 the commencement of the waves ; none are pro- 

 duced during the decreasing phase of each wave, 

 or at least if they are produced they do not act 

 upon the electro-magnetic signal. 



From the preceding it should be inferred that 

 the currents, inducted by the torpedo-waves and 

 produced at the commencement of these waves, 

 must in that be analogous to the inducted cur- 

 rents resulting from the completion of a galvanic 

 circuit. 



No instrument could be better than Lippmann' s 

 electrometer for giving us information as to the direction 

 of the currents inducted by the torpedo waves. Its instan- 

 taneous action enables it to indicate, by a sudden dis- 

 placement in a determinate direction, the direction of each 

 inducted current. 



If a weak current derived from the main discharge is 

 passed through the electrometer, we see the column after 

 moving to one side of the reticule always oscillate to the 

 same side, thus showing that the successive waves are 



Fig. 8. 



joined one to another, so that there is never an absolute 

 break in the current. In Fig. 9 the arrows show the 

 oscillation of the column towards the right side. 



If the induced currents are directed through an electro- 

 meter by the discbarge which causes the column of the 

 instrument to deviate to the right, the direction of oscil- 

 lation is immediately reversed (Fig. 10). 



The comparison of those two diagrams showing that 

 the inducted current has a contrary effect to that of the in- 

 ducting current, brings together the inducted currents of 

 the torpedo and those obtained by completing a galvanic 

 circuit. To be more exact, since the circuit which com- 

 prises the torpedo remains always complete, we shall say 

 that the inducted currents are produced at the beginning 

 of each electric wave of the animal. Thus the torpedo 

 calls forth in each of its electric waves an initial inducted 

 current and does not give a terminal inducted current. 

 This conclusion goes to support what we learned from 

 the wave-writing of the electro-dynamograph, viz., that 

 the initial phase of each wave has a suddenly increasing 

 intensity, whereas the terminal phase presents a gradual 

 decrease. 



5. The discharge of the torpedo is analogous to muscular 

 tetanus J every electric wave in the discharge corresponds 

 to a muscular shock. 



» Confnucd from p. 297." 



In what precedes we have endeavoured to give an idea 

 of the torpedo discharge from the nature of the suc- 

 cessive acts which constitute it, insisting only upon points 

 relating to experimental science and to the direct results 

 of M. Marey's investigations. 



We are now enabled to meet the question on higher 



Fig. 9. Fig. 10. 



ground and consider the electricj function from a philo- 

 sophical point of view, by classing it with the muscular 

 function. 



Let us first compare the elementary action of electric 

 discharge "to the elementary action of muscular contrac- 

 tion, i.e., the electric wave to the muscular shock. 



