STIMULATION OF MUSCLE AND NERVE 99 



sart. 



e.c. 



In frogs used during the period of hibernation 

 and especially in those brought from a cold store- 

 room into a warm laboratory, the make and some- 

 times the break of the constant current may be 

 followed by prolonged 

 tetanus. In such frogs, 

 the irritability of the 

 muscles is greatly 

 increased, and the 

 changes, probably 

 ionic, which occur 

 while the current is 

 passing and after it is 

 shut off are sufficient to 

 produce contractions 

 not seen in the normal 

 state (see page 147). 

 Usually the muscle is 

 stimulated only by a 

 sudden change in the Fi s- 26 - Hiud limb of fr s. anterior 



view (Ecker-Wiedersheim). 



intensity of the current. 



Changes in Intensity of Stimulus. Connect 

 one of the electrodes used in the preceding ex- 

 periment with one of the poles of a dry cell. 

 From the other pole lead a wire to a bowl of 

 salt water. To the other side of the same bowl 

 bring a wire from the remaining electrode. 



When the wires are slowly brought nearer 



t.p 



