RATE OF NERVE CONDUCTION. 227 



Clamp the nerve muscle preparation into position and lay 

 the nerve across the electrodes (2-5 cm -) as in the Figure. If 

 very long dispose it in a curve, and its length can be sub- 

 sequently measured. 



All being ready and the stimulus to the nerve having been 

 tested in both positions of the commutator, 



Perform the experiment as follows : 



1. Keeping the S key closed start the drum apply the 

 style to the paper, the rate should be such as to draw 

 the 96th second trace interval to not less than 1 cm \ Adjust 

 the speed accordingly. Make this trial at the bottom of the 

 paper. 



2. Apply the muscle recorder and style to the paper over- 

 lap and adjust them to write above each other, lift them 

 off. Mark the paper over-lap. 



Start the drum and inscribe an abscissa and time record 

 during one revolution of the drum, being careful to remove 

 the points before the next revolution begins. 



Let the drum continue to revolve from this onwards until 

 the experiment is complete. 



3. Two successive muscle tracings will now be taken on 

 immediately succeeding revolutions of the drum, the one as 

 the result of stimulating at a, and the other at b. This is 

 materially facilitated if your co-worker takes charge of the 

 commutator, and turns it over the moment you give the 

 signal that the first record is complete. 



Lift off the points the moment the second record has been 

 taken, and stop the drum. 



Next measure the interval between the two muscular con- 

 tractions. This interval is best measured about midway in 

 the ascent of the curves where they are clear of each other. 



