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HAND-BOOK OF PHYSIOLOGY. 



does not continue during the whole of the period when the primary cir- 

 cuit is complete. When, however, the primary current is broken by 

 opening the key, a second, also momentary, current is induced in g. The 

 former induced current is called the making, and the latter the breaking 

 shock; the former is in the opposite to, and the latter in the same direc- 

 tion, as the primary current. 



The induction coil may be used to produce a rapid series of shocks by 

 means of another and accessory part of the apparatus at the right of the 

 figure. If the wires from a battery are connected with the two pillars by 

 the binding screws, one below c, and the other, , the course of the cur- 

 rent is indicated in Fig. 279, the direction being indicated by the arrows. 



FIG. 279. Diagram of the course of the current in the magnetic interrupter of Du Bois ReymoncTs 

 induction coil. (Helmholz's modification.) 



The current passes up the pillar from e and along the spring, if the end of d' 

 be close to the spring, and the current passes to the primary coil c, and 

 to wires covering two upright pillars of soft iron, from them to the pillar 

 , and out by the wires to the battery; in passing along the wire, 1), the 

 soft iron is converted into a magnet and so attracts the hammer,/, of the 

 spring, breaks the connection of the spring with d' and so cuts off the 

 current from the primary coil and also from the electro-magnet. As the 

 pillars, #, are no longer magnetized the spring is released and the current 

 passes in the first direction, and is in like manner interrupted. At each 

 make and break of the primary current, currents corresponding are in- 

 duced in the secondary coil. These currents are, as before, in an opposite 

 direction, but are not equal in intensity, the break shock being greater. 

 In order that the shocks should be about equal at the make and break, a 

 wire (Fig. 279, e') connects e and d', and the screw d' is raised out of reach of 

 the spring, and d is raised (as in Fig. 279), so that part of the current 

 always passes through the primary coil and electro-magnet. When the 

 spring touches d, the current in Z is diminished, but never entirely with- 

 drawn, and the primary current is altered in intensity at each contact of 

 the spring with d, but never entirely broken. 



