102 GENERAL PROPERTIES OF LIVING TISSUES 



water. When thoroughly cold, place the muscle 

 in the Gaskell clamp (Fig. 26), making very 

 gentle pressure across the middle, and bring the 

 non-polarizable electrodes against the ends. Make 

 and, after a minute, break the current. 



The excitation wave passes so slowly through 

 cooled muscle that the contraction can be seen 

 with the unaided eye to begin at the cathode on 

 closing and at the anode on opening the circuit. 



3. Ureter. 1 Place the extirpated ureter of 

 any mammal on a glass plate set as a cover on 

 a beaker containing hot normal saline solution, 

 so that the hot vapor of the water shall keep 

 the ureter warm. Bring the non-polarizable 

 electrodes against the ureter. Note which elec- 

 trode is the cathode. Close the key. 



After a distinct latent period the ureter in the 

 cathodal region, and nowhere else, will contract, 

 and the contraction wave will spread from the 

 cathode in both directions along the ureter. 



Open the key. 



The Gaskell Clamp. The tapered edge of a hard- 

 rubber block is brought against a similar edge by 

 means of a fine screw (Fig. 26). With this clarnp 

 the heart muscle may be compressed, after Gaskell's 



1 The experiment succeeds also with extirpated pieces of in- 

 testine about four inches long, provided they are kept warm 

 with normal saline solution. 



