INDUCED ELECTRICITY. 35 



helix than from tliat of the second. These experiments are not 

 harmless ; because in many cases the acute sensations have been 

 followed by neuralgic pains in the organs over-excited. The 

 difference in the action of the two currents upon the sensibility of 

 the retina is far from being as great as in the preceding cases ; but 

 I have seen many persons who have been inconvenienced by bril- 

 liant phosphenes, produced by the current of the second helix, 

 when I have excited regions supplied by the branches of the tifth 

 pair, such as the face or the tongue. Patients have been even 

 fearful about their sight, and have complained of muscae volitantes, 

 after such operations. 



These facts show, therefore, that the currents of the two helices 

 must not be employed indifferently or indiscriminately ; and that 

 the practitioner must be circumspect in the selection of one or the 

 other of them. 



B. — Cases in ivJiich we should em]ploy hy preference the current of 

 the first or of the second helix. 



The differential action of the currents of the two helices being 

 known, it is easy to foresee in what cases the one or the other 

 should be chosen. 



The extreme energy with which the current of the second helix 

 acts upon the sensibility of the skin, renders it a most valuable 

 agent in the treatment of cutaneous ansesthesia, or in producing 

 a cutaneous revulsion or shock greater, if desired, than that 

 of the actual cautery, without any destruction of tissue, e.g., in 

 rheumatoid and neuralgic affections. It is unnecessary to add 

 that the current of the second helix will succeed in a number of 

 cases in which that of the first would be AvhoUy powerless. I have 

 frequently seen cutaneous anaesthesia yield rapidly to the current 

 of the second helix, when an apparatus possessing only the cur- 

 rent of the first helix more powerful than the former in exciting 

 muscular contraction, had failed to exert upon it any appreciable 

 influence ! 



If it be desired to practise electric excitation ujDon deep masses 

 of muscle, protected by thick aponeuroses or covered by an adipose 

 subcutaneous cellular tissue, thick or oedematous, the current of 

 the second helix perfectly fulfils the indication, by virtue of its 

 greater tension ; or, in other words, on account of its power of 

 penetration. 



Again, the current of the second helix, which acts less upon the 

 muscular sensibility than that of the first, should be preferred 

 when it is desired to provoke energetic contraction with as little 



D 2 



