STIMULATION OF MUSCLE AND NERVE 141 



The same is true of the ureter (Engelmann). 



4. Tonic Contraction. Examine the contrac- 

 tion curve already recorded by the smooth 

 muscle of the frog's stomach. Note that the 

 muscle remains contracted during the passage 

 of the current. The curves secured from the 

 curarized sartorius (page 139) also show this, 

 but to a much less degree ; the sartorius does 

 not resume its former length after the twitch or 

 closure of the galvanic current, but remains con- 

 tracted to a slight extent. This tonic contrac- 

 tion appears much more plainly in fatigued 

 muscles. 



Fatigue a sartorius muscle by stimulating it 

 with a galvanic current repeatedly made and 

 broken. After a time, the twitch on closure will 

 become very feeble, and finally will disappear, 

 while the tonic shortening during the passage of 

 the current is still very evident. 



5. The influence of duration is shown also in 

 the opening contraction. 



Fasten the pelvic attachment of a sartorius 

 muscle in the muscle clamp and connect the 

 other end with the upright pin of the muscle 

 lever, so that the horizontal muscle shall record 

 its contraction on a drum. Place the non-polar- 

 izable electrodes on the ends of the muscle. 

 Allow the galvanic current from a dry cell to 



