306 PHYSIOLOGY OF MUSCLES AND NKI;\ I -. 



Occasion. illy i' is de-iral'le to remove this difference, and 

 to provide two inductive currents which flow and act nearly 

 in the same way. This may L- inanagi d. if, instead of 

 rlo-ing and interrupting the current of the primary coil, an 

 additional closing wire offering small resistance is provided, 

 ami tlit- interruption is effected in this. If this additional 

 apparatus is present, only a very small part of the current 

 passe.> through the primary coil. The strength of this part is 

 indicated by 7, i/,. "When the closing in the additional ap- 

 paratus i.s inten upied, the primary curr. nt slowly incre.-i- 

 in strength from J ' , to J as shown by the dotted curve ." ; 

 with this incivas corresponds an inductive current in the 



'iidary coil, as represented by curve 6. If the closing of 

 the additional apparatus is once more effect d. the current in 

 the primary coil sinks in strength from J to J -, but tbe so- 

 calle 1 >:.<-tr<i cttrr-'nf, that, which originates in consi-tpn-nce of 

 the sinking in the primary coil, is now able, the coil being 

 closed, to take riled, and, as its direction is the same as that 

 of the main current, it retards the sinking of the litter, so 

 that this now takes place as indicated l>y curve 1 ( and with 

 this slow sinking of the miin current c.irre-pnnds an induc- 

 tive current in the s r'jnd-iry coil, siu-h as is shown )>y 

 curve 8. 



Helmholu mule an alteration in du I'.oi- lleyniond's 

 sliding inductive apparatus by means of which this ad- 

 ditional closing and opening is automatically arc-implNied. 

 lie adapted Wagner's hammer for this purpose, as shown in 

 Jig. 71. The current of the apparatus A' pa-i-rs through tin- 

 wire arranged ln-tween ;i and /' to the jirimary coil c. from 

 this to the Coils round the small electromagnet /', and fi-om 

 the latter through the column n. Lack to its original starting 

 piint. The electro magnet attracts the hammer //, in con- 

 si'ijuence ut' which a small platinum plate fastened Lelow 

 the < leriirm silver spring is Lrought into contact with the 

 platinum ]niint of (lie screw/, thus ci.mplrting a Lrief and 



flljcirnt additi"l'a! cl. ..-,11 re // / u. Tlir curisi ( jlli 'lice . .f this 



