56 INDUCTION SHOCKS 
In order that the final stimulation units may be of 
convenient size the value of L which has been adopted 
in this scheme is not the direct product of the cross 
section by the number of turns of the secondary, but is 
that product divided by 100. Having determined this 
value, the mutual inductions previously established are 
divided by it. The resulting figures are the " calibra- 
tion numbers" for the particular secondary positions to 
which they apply. To determine the numbers for in- 
termediate positions those determined as above are plot- 
ted on a rather large scale on coordinate paper and a 
smooth curve is drawn connecting them. Since the 
mutual induction necessarily diminishes, not by fits and 
starts, but smoothly, as the secondary is moved out- 
ward, such a curve, if carefully made, will indicate the 
calibration numbers for intermediate positions with a 
high degree of accuracy. 
To prove the accuracy of the calibration the method 
of v. Fleischl is employed (p. 18) in which the minimal 
contraction of a frog's gastrocnemius is used as the index 
of a constant stimulus. In detail this procedure as carried 
out by myself was as follows : The freshly isolated gas- 
trocnemius was suspended by its attached femur in a 
moist chamber, and its lower end connected by a small 
copper wire to a muscle lever whose effective weight was 
about 10 gm. ; the muscle was not afterloaded. The lever 
had a magnification of about ten, and its point pressed 
