NERVE. 



53 



arranged in a moist chamber with the nerve lying on a pair oi 

 electrodes in cork near the muscle and a pair of boot electrodes 

 farther out. Adjust the induction coil so that a break shock 

 just causes contraction of the muscle through the electrodes 

 in cork. Record the height of this contraction either on a 

 slow or stationary drum. Next connect the boot electrodes 



FIG. 16. Top view of moist chamber in the preceding figure, showing the 

 arrangement of the electrodes (c) from the secondary coil in relation to the boot 

 electrodes. Nerve (h) is shown across the two sets of electrodes. (6) connects with 

 secondary, (a) connects with direct current supply. 



to the current from the rheostat so that the kathode is nearer 

 the muscle. Try two volts at first. Determine which boot is 

 kathode and which is anode by dipping the two wires into 

 NaCl solution ; bubbles of hydrogen will issue from the kathode. 

 While the constant current is flowing through the nerve by 

 way of the boot electrodes, stimulate the nerve with the same 



