24 LOCALIZED ELECTRIZATION. 



points of emergence of branches of tbe trifacial nerves, or on 

 tlie eyeball itself. The flame then perceived is paler than that 

 from the current of the second helix of tlie electro-magnetic 

 instrument, and imp'resses the retina less vividly. The current of 

 the first helix of the electro-magnetic instrument produces no 

 more impression of liglit than that of the electro-dynamical instru- 

 ment. Lastly, the luminous sensation that is due to the action of 

 the current of the second helix of the electro-magnetic apparatus 

 is far from being so strong as that which is excited by electro- 

 ^^otor instruments. 



B. — The current of tlie second helix excites the cutaneous sensibility 

 more vivicllij than the current of the first helix. 



This phenomenon was established as follows : — Two electro- 

 dynamic or electro-magnetic instruments were set in action, so 

 arranged that one furnished the current of the first, the other 

 the current of the second helix ; and they were so graduated 

 as to act with equal force upon muscular contractility. If then 

 the skin was excited by these alternately, it was always observed 

 that the sensation produced was much less, under the influence 

 of the current of the first helix than under that of the second. 



Such are the differential properties of the currents of the first 

 and of the second helices, properties the discovery of which goes 

 back to 1848, which I described to the Academy of Sciences in 

 1849, and which were set forth in the former edition of this work 

 in 1855. Since then, my experiments upon the differential pro- 

 perties of induced currents having been facilitated by the use of a 

 commutator of the helices that I have added to my instruments, 

 by which I can change rapidly from one current to another, and 

 more readily compare their physiological effects, I have observed 

 that the induced currents possess other special properties of no 

 less physiological and therapeutical importance. These I proceed 

 to describe. 



C. — The current of the first helix excites, more poiverfuUy than that 

 of the second, the sensihilitij of certain organs 'placed more or less 

 deeply beneath the skin. 



I was led to a knowledge of this fact while repeating, in the 

 presence of M. Beclard, Associate Professor of the Faculty of 

 Medicine, the experiments that display the differential properties 

 of currents, and that I have described above. My learned com- 

 panion observed to me that the current of the first helix produced 

 in him a much more acute sensation than the current of the 



