310 THE OUTGO OF ENERGY 



electrodes over the brachial plexus in the axilla. 

 Bring the meniscus into the field. Open the 

 short-circuiting key leading to the electrometer. 

 If the meniscus is displaced by a skin (secretion) 

 current bring it back by means of the pressure 

 apparatus. Set the inductorium in action. Open 

 the short-circuiting key of the secondary coil, 

 thus stimulating the nerves. 



The meniscus will be displaced by an action 

 current. 



Action Current of Heart. 1. Expose the 

 heart of a frog (page 112). Lay the nerve of an 

 irritable nerve-muscle preparation on the beating 

 ventricle. 



During diastole, the rheoscopic muscle will be 

 quiet ; at each systole, it will contract. 



2. Tie a cotton thread one inch long about the 

 foot of each non-polarizable electrode, and let 

 the ends, wet with normal saline solution, rest 

 on the beating heart, one on the base, the other 

 on the apex. These electrodes will follow the 

 movements of the heart. Connect the elec- 

 trodes through a short-circuiting key to the 

 electrometer. 



During the diastole, the meniscus will remain 

 at rest. At each beat of the ventricle, the 

 meniscus will move ; first in a direction indicating 

 that the base is negative to the apex, and then 



