STIMULATION OF MUSCLE AND NERVE 143 



the ventricle transversely. Eest this "apex" 

 preparation between the tips of two non-polar- 

 izable boot electrodes. Keep the tissue moistened 

 with normal saline solution, but avoid excess. 

 Close the key. Move the slider along the wire. 



When the current taken off reaches the thresh- 

 old value, the apex will begin to beat rhyth- 

 mically. Increasing the current strength will 

 increase (within limits) the frequency of con- 

 traction. 



Skeletal Muscle. The curarized sartorius may 

 sometimes be brought into rhythmic contraction 

 by constant currents (Hering). If the irrita- 

 bility of the muscle at the point of stimulation 

 be increased by applying to the cathodal region 

 a two per cent solution of sodium carbonate, the 

 constant current will- produce strong rhythmic 

 contractions. 



Smoke a drum. Fasten the pelvic end of the 

 sartorius in the muscle clamp, and attach the 

 tibial end by a thread to the vertical pin on 

 the muscle lever so that the horizontally extended 

 muscle may write its contraction on a drum. 

 Lay on the tibial fifth of the muscle a piece of 

 filter paper, wet with two per cent solution of 

 sodium carbonate. Connect a dry cell through 

 a simple key with the metre posts of the rheo- 

 chord. Connect the non-polarizable electrodes 



