30 



ADVANCED LESSONS IN PRACTICAL PHYSIOLOGY 



binding-posts which, in turn, may be connected with the stimulating 

 electrodes. These connections constitute the secondary circuit of the 

 inductorium. As has been stated above, the making and breaking of 

 the primary current gives rise momentarily to an induced current in 

 the secondary coil. 



A rapid interruption of the primary current may be effected by 

 closing and opening the key in quick succession with the hand. A 



^% i, > w ' **** 



FIG. 8. THE INDUCTORIUM. 



/, Primary circuit and coil; //, secondary coil and circuit; K, key; /, automatic inter- 

 rupter; n, nerve. 



more convenient means, however, is afforded by such automatic inter- 

 ruptors as have been described by Neef. The latter mechanism con- 

 sists of a vibrating rod and magnet, both of which are attached to the 

 end of the inductorium. A glance at Fig. 10 will show that the current 

 from the battery (A) is led into pillar B as far as the platinum contact 

 D upon the vibrator V. If the latter is in contact with the end of the 



FIG. 9. THE INDUCTOBIUM. (Harvard Apparatus Co.) 



wire of the primary coil at D, the current will traverse this spiral (PC) 

 and return to pillar F and the battery by way of the double spiral E. 

 But as the current passes through spirals E their iron cores are mag- 

 netized and attract the iron plate H of the vibrator V, thereby break- 

 ing the contact at D. When the primary current is broken in this 

 manner the spirals (E) are again demagnetized. This plate (H) being 

 released, the vibrating rod moves upward and again makes contact 



