80 



The electromotive force of the currents in the secondary 

 bears a direct relationship to the primary. Thus, if there are 

 200 turns in the P and 6000 in the S, the electromotive 

 force of the induction currents would be about thirty times as 

 great as the primary, independently of the influence exerted 

 by the iron core. 



311. Connect the Secondary Circuit of the Induc- 

 TOBiuM. It is well to do this first in all cases. Fasten a key 

 to the table close to the left end of the machine as it now 

 rests upon the table, and connect the binding- screws of the S 

 coil with those of the key by means of two wires, so that 

 when the key is closed the S circuit is thereby also closed. 

 This is the short circuiting key in the secondary circuit. 



Fig. 13 Fig. i4 



Fig. 13 — Key closed. Fig. 14 — Key open. 



Now attach the long circuit wires by means of which the 

 connection is to be established, with the seat of stimulation, 

 i. e., attach the electrodes by their metal tags to the other 

 pair of binding screws of the key. 



312. Connect the P Coil for Single Induction Cur- 

 rents. Place the battery upon the table near the right hand 

 end of the coil and attach a key to the table close to it ; keep 

 the key open. In making the connections always begin at the 

 battery, and follow the direction the current will take. 



Connect the C (carbon) pole of the cell to the key by a 

 wire, then wire the other side of the key to the top binding 

 screw a, fig. 11, of the P coil, wire b to the zinc pole of the 

 cell. 



Withdraw the S coil to the end of the scale and let one 

 co-worker hold the electrodes to the tip of the tongue or to a 

 nerve muscle preparation, whilst the other makes the trials. 



