VOLUNTARY MUSCLE. 



17 



THERMAL. Touch the fresh end of the nerve with a hot glass 



rod. 



ELECTRICAL. Connect the stimulating electrodes directly to 



the current supply on the table but with a simple key in the 



circuit. Try the effect of make and break, beginning with 2 



volts and then increasing the current. 



FIG. 2. Apparatus for recording muscle contraction: (a) femur clamp; (6) nerve holder 

 (c) electrodes; (d) muscle lever; (e) signal magnet; (/) after-loading screw; (g) wires connected in 

 the primary circuit. 



Next connect the electrodes to the secondary coil of the 

 inductorium using a primary current of 2 volts; stimulate with 

 make and break shocks of different intensities. 



Compare the effects of make and break in direct and indirect 

 currents. 



Minimal and Maximal Stimulation. Beginning with a 

 stimulus too weak to cause contraction, then very gradually 

 increasing its strength, a point is reached where a slight contraction 



