74 GENERAL PROPERTIES OF LIVING- TISSUES 



5. It is not even necessary that the conductor 

 should be actually in contact with the prep- 

 aration. 



Connect a nerve-muscle preparation, insulated 

 on a glass plate, with one pole of the secondary 

 coil, and set the inductorium in action. The 

 secondary coil should completely cover the pri- 

 mary. Bring a moistened ringer as near the 

 muscle as possible without touching it. 



With the proper intensity of the primary cur- 

 rent, contraction will take place, though absent 

 when the finger is removed. 



The sudden approach of a condenser charged 

 with static electricity will stimulate an isolated 

 nerve or muscle. 



6. The danger of error from unipolar action is 

 particularly great in electrometer observations on 

 the current of rest or action current of nerve and 

 muscle, discussed and demonstrated experiment- 

 ally in Part III, Chapter II. 



The errors due to unipolar action can usually 

 be prevented by the following precautions : The 

 secondary coil should always be connected with 

 the tissue to be stimulated through a short- 

 circuiting key, which should be kept closed ex- 

 cept during the intentional stimulation of the 

 tissue. With this good metallic connection be- 

 tween the ends of the secondary wire there will 



