260 LOCALIZED ELECTRIZATION". 



the muscular contraction which it produces appears to be con- 

 tinuous. The sj)ecial properties of this very rapid movement, and 

 the energetic influence that it exerts upon sensibility, have induced 

 me to adopt it as a valuable resource in the investigation of 

 certain electro-j)hysioIogical phenomena, and in the treatment 

 of certain dynamic lesions. But the necessary mechanism cannot 

 always replace the toothed wheel or the pedal, because it may, in 

 some cases, produce even serious accidents. I hold, therefore, that 

 every instrument should be furnished with both a pedal and a 

 trembler. 



The common forms of trembler — all of which I have studied — so 

 often become out of order, and, so to speak, stop so capriciously, 

 that it would be necessary to abandon their application to in- 

 duction instruments, if these imperfections could not be overcome. 

 It has often occurred to me, with certain instruments, to be unable 

 to proceed with an exj)eriment, or a therapeutical application, on 

 account of the stopping or the irregular action of the trembler, — 

 an apparent caprice, the cause of which I could not immediately 

 discover. 



By increasing the power of the magnetization of the soft iron of 

 the core, and of the movable piece of iron which produces the 

 intermissions^ and by rendering the vibration more simple and 

 easy by a proper adjustment of the force of the spring to the 

 weight of the movable iron, I have now so well regulated the 

 action of the trembler that it never fails, in my instruments, if 

 the power of the pile be sufficient. 



Tremblers may be made with or without vibrations. The 

 tremblers with vibrations are those which, between the inter- 

 missions, undergo rapid recoils or rebounds, which render faradiza- 

 tion very unpleasant. 



The more painful sensation produced by the trembler with 

 vibrations renders certain experiments on the muscles more 

 difficult, even when only a moderate dose is employed. This 

 trembler, however, may be very useful in cases in which it is 

 desired to excite sensibility and nutrition very acutely. 



I have contrived a trembler of which the beats may be quickened 

 or retarded at pleasure, so that it may give as few as four inter- 

 missions in a second, or an incalculable number, passing through 

 all intermediate degrees of rapidity. I have adapted this trembler 

 to my uncovered instrument (fig. 56). 



Fig. 57 offers a front view of this apparatus, showing the 

 trembler. One of the extremities of the wire of the primary coil 

 communicates with the knob E, the other with the screw C. The 

 movable piece of copper, A, which is pressed back by a spring 



