GENERAL PHYSIOLOGY. 



(2) To change the course of the current. Set up 

 apparatus with cross bars removed, as shown 

 in PI. I Fig. 4. What course will the current 

 take when the bridge is turned toward a, b? 

 What course when the bridge is turned toward 



c, d? 



(3) Pohl's commutator may be used as a simple 

 mercury key (PI. I Fig. 5V Is the current open 



FIG. 3. 



FIG. 

 The mercury key. 



FIG. 4. 



FIG. 4. The DuBois- 

 Reymond key. 



or closed when the commutator bridge is turned 

 toward a? How may the current be opened or 

 broken? 



d. Work done by the cell. The experiments performed 

 show that the galvanic cell may under proper con- 

 ditions, liberate energy. This energy is called elec 

 tricity. But the immediate source of the particular 



