320 THE OUTGO OF ENERGY 



Errors from Unipolar Stimulation. Attention 

 already has been called to the danger of unipolar 

 induction currents entering the electrometer 

 circuit in observations of the action current with 

 the capillary electrometer or galvanometer (page 

 74). 



Place a nerve in the moist chamber. Connect 

 the capillary electrometer through a short-circuit- 

 ing key with non-polarizable electrodes placed on 

 the longitudinal surface and cross-section, about 

 5 mm. apart. Let a wire connected with one 

 pole of the secondary coil rest on the nerve about 

 2 cm. from the non-polarizable electrodes. Open 

 the short-circuiting key. When the meniscus 

 has come to rest, set the inductorium in action. 



If the meniscus remains at rest, bring the 

 secondary coil nearer the primary, until unipolar 

 effects appear. 



SECRETION CURRENT 



Secretion Current from Mucous Membrane. 



Remove the skin from the lower jaw of a frog, the 

 skull of which has been cut away. Be very care- 

 ful not to touch the tongue with metal instruments 

 or with fragments of skin. Make a normal saline 

 clay electrode about 1 cm. square and 3 mm. 

 thick on the glass of the cork clamp near the 



