122 ELEMENTARY PHYSIOLOGY. [XI. 



3. By means of a longitudinal incision divide the 

 auricles with the attached portions of ventricle 

 into two lateral halves. Each half will continue 

 to beat. 



III. Cilia. 



Placing the frog on its back, cut through the 

 lower jaw, in the middle line, and carry the 

 incision down the oesophagus as far as the 

 stomach. Pin back the parts and moisten the 

 mucous membrane, if it is at all dry, with 

 normal saline solution. Place on it, a little 

 below the orbits, a small thin piece of cork. 

 The cork will be seen to be driven by ciliary 

 action down towards the stomach. 



DEMONSTRATIONS. 



1. The electric currents of nerves removed from the 

 body (demarcation currents). 



2. The negative variation attending a nervous 

 impulse (action current), 



3. The effect of a constant current on demarcation 

 currents (electrotonus). 



4. The effect of a constant current on the irritability 

 of nerves (electrotonus as affecting irritability). 



5. The law of contraction. 



