HISTORY, &c., OF INDUCTION INSTRUMENTS. 307 



appears to have readied the farthest limits of possibility in this 

 direction,"^ 



§ II. — Critical examincCtion. 



The account of the principal electro-medical instruments, in 

 their chronological order, which has been given in the preceding 

 pages, and which has been in great part quoted from the excellent 

 memoir of M. Le Roux, has brought sufficiently into relief their 

 successive improvements, at least from the physical point of view. 

 But do they fulfil the requirements of localized faradization, as 

 applied either to the electro-muscular experiments (which, in my 

 researches, have thrown so much light upon the physiology of 

 locomotion), or to electro-muscular testing (which often decides 

 the diagnosis of so many mnscular affections), or to the treatment 

 of disorders of the central or peripheral innervation, of sensibility, 

 of motility, or lastly, of nutrition ? To decide such a question, it is 

 necessary to possess some anatomical and physiological knowledge, 

 and to have acquired, at the bedside of patients, sufficient practical 

 experience. 



The physicist whom I have quoted (M. Le Roux) has wisely 

 kept silence upon the point ; thus implicitly declaring himself 

 incompetent to deal with a purely pliysiological and medical 

 question. In order to ascertain whether all induction instruments 

 possess the whole properties which would render them applicable 

 to the electro-physiological and clinical studies which I have 

 described, and to the fulfilment of certain therapeutical indica- 

 tions, I must inquire whether they have been constructed with the 

 physical and mechanical conditions necessary for the attainment 

 of these properties ; or, that is, whether they possess, — 1. a double 

 induction ; 2. an exact graduation ; 3. intermissions, rapid or 

 slow at pleasure ; 4. a sufficient degree of force ? The considera- 

 tions which I have already stated with regard to the utility of 

 these conditions, which all electro-medical instruments should 

 combine, render it unnecessary for me to enter upon the subject 

 anew. It will be enough to state briefly the principal facts upon 

 which my critical examination will be based. 



1. Magneto-electric instruments. 



(A). Double induction. — Whatever may be the physical theory 

 of the phenomena of double induction in magneto-electric instru- 

 ments — a theory on which physicists will, I hope, before long 

 agree, — it cannot now be denied that the currents which proceed 



= Le Eoux, p. 63. 



X 2 



