292 THE OUTGO OF ENERGY 



rent. A long series of contractions may be 

 secured. Other liquid conductors will serve. 

 When the solution touches only the cross-sec- 

 tion, there is no contraction. 



4. Prepare a fresh sartorius muscle with bony 

 attachments. Fasten the pelvic end in the 

 muscle clamp. Make a fresh cross-section in 

 the first sartorius. Hold the tibial end of the 

 second muscle in such a way that the muscle 

 lies horizontally with its upper surface some- 

 what concave. Against this surface bring the 

 fresh cross-section of the first sartorius. The 

 longitudinal surface will naturally also touch 

 to some extent. 



The second muscle will close the circuit be- 

 tween longitudinal surface and cross-section of 

 the first, and, if very irritable, both muscles will 

 contract. 



Interference between the Demarcation Current 

 and a Stimulating Current ; Polar Refusal. Con- 

 nect a dry cell through an open key with the 

 and 1 metre posts of the rheochord (Fig. 46). 

 Mount two non-polarizable electrodes, and con- 

 nect them through a pole-changer (with cross- 

 wires) to the positive post and slider of the 

 rheochord. Tie a thick cotton thread to the 

 foot of the positive electrode in such a way 

 that the thread shall hang down in a small loop. 



