266 LOCALIZED ELECTEIZATION. 



to be aware when this occurs, because the power may be diminished 

 considerably. 



H. — The Commutator of the Poles. 



It is useful to be able rapidly to change the direction of the 

 currents, without displacing the rheophores from their position on 

 the patient. For this purpose, I have fitted to my covered instru- 

 ment a commutator of the poles (H, fig. 55), which, by turning to 

 the right or to the left, changes their direction. Its mechanism 

 is the same as that of the commutator of the currents. 



Part the Third. 



SMALL DOUBLE-CURRENT VOLTA-FARADIO APPARATUS. 



This instrument, with medium force, possesses all the properties 

 required in a medical apparatus. It is a reduction of my large 

 double-current volta-faradic instrument ; and is generally capable 

 of replacing it in practice. 



A. — Description. 



I have given to this apparatus the form of a flat oblong box, or 

 of an octavo volume, as shown in fig. 58. When it is open, as in 



Fig. 59.— Soft iron. 

 — — , ~'n 

 H H' 



Fig. 58. — Author's small volta-faradic apparatus (closed). 



fig. 60, it is seen to be divided into two parts. To the right is 

 placed the induction apparatus properly so called. To the left 

 is the battery, in the lower compartment A ; and the rheophores, 

 with their conductors, are in the upper compartment B. 



The induction apparatus is composed : — 



1. Of a reel, six centimetres in length, formed by two super- 

 posed coils, the wires of which are of different length and diameter 

 (the wire of the primary coil is sixty metres in length and a half 



