SINGLE MUSCULAR CONTRACTION. 213 



Set up as follows : Arrange for single shocks, connect the 

 S circuit to the outer terminals of the muscle chamber and 

 substitute the fine wires for the electrodes. Clamp the muscle 

 into position and attach it to the writing arm, and make 

 one of the thin wires fast to the femur, and the other to 

 the tendon; the second wire must not constrain the muscle. 



Choose single induction shocks to produce strong contractions. 



Take only the break shocks, e.g., close the S key each 

 time before closing the P circuit, and open the former again 

 before the P circuit is opened. These evolutions should be 

 performed in rapid succession, so as not to keep the P 

 circuit closed for long (to ensure equal stimuli). 



Apply a weight, let the muscle extend fully, turn the 

 drum by hand some 7 mm , stimulate the muscle; it will draw 

 an upstroke and will on relaxation be extended below the 

 line from which it started. Turn the drum onwards for 

 the same distance as before, add another weight and repeat 

 the process until all the weights have been added. 



Examine the tracing and compare the passive extension 

 due to the application of the weight with that which 

 accompanies relaxation after each contraction. 



Single muscular (isotonic) contraction and latent 8 

 period, with direct excitation of the muscle. 



Required: Muscle chamber on stand, inductorium, electric style, 

 2 Leclanche cells, 3 keys, 10 wires (two of them fine). Drum to fastest 

 speed. Muscle load lO* 



1. Set up for single induction shocks and include the drum 

 contact in the P circuit. See that the contact is very slight, 

 so that the make and break shocks may be fused into a 

 single stimulus. Keep S key closed until the time of stimula- 

 tion. Detach the platinum electrodes from their binding screws 

 in the muscle chamber and substitute the fine wires for them. 



