100 GENERAL PROPERTIES OF LIVING TISSUES 



together, there will be no contraction ; when they 

 are brought quickly together, thus quickly in- 

 creasing the intensity of the current, the muscle 

 will contract. 



With Indirect Stimulation. 1. Smoke a drum. 

 Make a nerve-muscle preparation (sciatic nerve 

 and gastrocnemius muscle). Place the femur 

 in the clamp in the moist chamber. Let the 

 nerve rest on non-polarizable electrodes connected 

 through an open key with a dry cell. Attach 

 the tendo Achillis to the muscle lever. Let the 

 muscle lever write on a slowly moving drum. 

 Close and open the key. 



Both closing and opening contraction will be 

 seen. (If the frog has been brought from a cold 

 room into the warm laboratory, opening and 

 closing tetanus will probably replace the usual 

 twitch. See page 147.) 



2. Eepeat the experiment on page 99, using 

 the nerve-muscle preparation instead of the 

 curarized muscle. 



It will again be found that the intensity of 

 the current must be increased with a certain 

 rapidity in order to stimulate. 



The experiments just made support DuBois- 

 Beymond's statement that the electrical current 

 does not stimulate during the entire period of 

 its flow through the irritable tissue, but only 



