THE ELECTROMOTIVE PHENOMENA 293 



Let a sartorius muscle rest on a clean glass 

 plate. Make an artificial cross-section by draw- 

 ing a hot wire across the muscle near the pelvic 

 end. Pass the loop of thread on the positive 

 electrode over the muscle about 5 mm. from the 

 thermal cross-section. Let the negative electrode 

 rest on the cross-section. Arrange the rheochord 

 for weak currents. Moisten the electrodes with 

 normal saline solution. Close the key. 



The usual closing contraction 

 will be absent (polar refusal). 



Note that the galvanic cur- 

 rent is now passing through 

 the muscle in an atterminal 

 direction, i. e. towards the in- 

 jured portion (admortal), while 

 the demarcation current is 

 passing through the muscle in Wg. 46. 



the opposite direction. The two currents more 

 or less compensate each other. Hence, the ab- 

 sence of the closing contraction. Observe, also, 

 that opening the key will break the galvanic cir- 

 cuit, but that the circuit for the demarcation 

 current will still be closed through non-polariz- 

 able electrodes and rheochord. 



Open the key. 



An opening contraction will take place, 

 obviously because the muscle current is no 

 longer compensated. 



