MUSCLE AND NERVE 



31 



at D. At the moment when the primary current is made and broken 

 an induced current is momentarily developed in the secondary coil. 



6. Stimulation of Muscle and Nerve The Constant Current. Con- 

 nect in series two dry cells and a simple key and apply the ends of the 

 wires leading away from them to the tongue. Make and break the 

 current by closing and opening the key. When do you perceive the 

 stimuli? Note that the make shock is the stronger of the two. Does 

 the current stimulate while it continues to flow, i. e. } between the make 

 and break? 



Upon the basis that a stimulus arises in consequence of any extra- 

 ordinary change in the environment, it may be said that an electric cur- 



FIG. 10. THE AUTOMATIC INTERRUPTER OF THE INDUCTORIUM (NEEF'S). 



A, Entrance of current from battery into post B and vibrator V as far as D. In 



accordance with the position of the vibrating plate, the current now flows either back to 



the battery C through post F or into the primary coil PC through Z>. In the latter 



case, the current first traverses magnet E before it can reach the battery by way of post F. 



rent stimulates only when its intensity is rapidly altered. Such altera- 

 tions occur only on the make and on the break of the current, and 

 hence, no stimulation is evoked in between these two points. Inasmuch 

 as the full electric potential is thrown into the living substance on the 

 make of the constant current, the latter reacts with greater amplitude 

 at this time than later on (break), when it has been partially adapted 

 to this stimulus. 



Single Induction Shocks. Connect in series two dry cells, a simple 

 key, and posts 1 and 2 of the inductorium. This connection does not 

 include Neef's automatic interruptor, and hence, the current may be 

 made and broken at intervals of varying length. Make and break the 



