DOUBLE-CURRENT MAGNETO-FARADIC APPARATUS. 275 



I am willing to bow before the great authority of M. de la Rive, 

 but I must nevertheless ask permission to remind him of an 

 experiment which he witnessed in my laboratory.'' He has, with- 

 out doubt, forgotten that I showed him, with the primary coil of 

 my double-induction instrument, the physiological power of the 

 extra current, comparatively, with and without the soft iron core. 

 We then saw that, under the influence of the magnetization of this 

 iron core, the power of induction of the extra current was increased 

 in a considerable proportion. Is it not reasonable to conclude 

 that, under these circumstances, the greater part, if not the whole, 

 of the power of the temporary magnetization was employed to 

 influence th.e primary coil, and thus to increase the energy of the 

 extra current ? But in order to admit, with M. de la Rive, that 

 the induced current, which is then developed in the completed 

 circuit of the superposed secondary coil, is precisely like that 

 which induces the direct action of the magnet, it would be neces- 

 sary, I think, to prove that the magnet then ceases to exercise its 

 influence upon the primary coil, which is the nearest to it, and 

 removes its action to the secondary coil, which is the most remote 

 from it. But I am not aware that this, wbich to me seems 

 improbable, has ever been demonstrated. 



It is after having made the foregoing experiments, and after 

 having interpreted them in this manner, that I think I am autho- 

 rized to formulate the following conclusions : — 



1. In the volta-electric instruments, the temporary magnetiza- 



* Before forming an opinion of the 

 value of my electro-phytiiological and 

 therapeutical researches, and especially be- 

 fore criticising them, this philosopher has 

 not only thoroughly studied what I have 

 written, but has also done me the honour 

 to seek from me explanations with regard 

 to my instruments. Then, experimenting 

 upon himself, I have been able to show 

 him tlie reality of the chief special or 

 ditferential physiological actions of the 

 currents of the primary or of the secondary 

 coils of these instruments. 



To the opinion of M. E. Becquerel, who 

 writes, " the extra current and the current 

 of the first kind do not possess elective pro- 

 perties over tins or that function, hut they 

 have an action more or less energetic, Inj 

 reason of their tension," it is interesting 

 to oppose that of M. de la Rive, who has 

 endeavoured to explain the difference be- 

 tween the physiological projDerties of the 

 two currents — a ditierence such that they 

 cannot be substituted for one another in 

 practice, and that depends, according to 

 him, not only upon the induced ciurent 



possessing greater tension than the extra- 

 cui'rent, but also uiwn its Ixing in general 

 more momentary, and, lastly, upon its 

 being composed of two currents passing 

 alternately iu contrary directions ; while 

 the extra current is composed of one 

 induced current only, passing always in 

 the same direction. 



" We mu.^t liere remember," says M. de 

 la Eive, " that we may have, between the 

 extra current and the current induced in 

 the second wire, other physical differences 

 than those relating to quantity or inten- 

 sity; and that hence, although we may 

 construct coils, in which, as regards tlie 

 last-named qualities, the currents shall be 

 alike, they may still dift'er from one an- 

 other. In the first jilace, the extra current 

 is never comi^osed of more than a single in- 

 duced current, which always passes iu the 

 same direction with the battery current, 

 while the induced current properly so- 

 called, is composed of two instantaneous 

 currents, parsing alternately in opposite 

 directions. This dilference njay well pro- 

 duce a difference of physiological action," 



T 2 



