34 INDUCTION SHOCKS 
Helmholtz' conclusion is not wholly valid. But at this 
stage of the discussion we may neglect the effect of the 
descending portion of the curve, and proceed as though 
the ascending limb were the sole determining factor. 
Since the chief physiological effect is exerted during 
the growth of the current this effect will be greater the 
higher the curve rises; in other words, the strength of 
stimulus tends to be proportional to the maximum in- 
tensity of the induced current. In the diagram, Fig. 10, 
the maximum intensity is represented by the ordinate 
CB, drawn from the base line to the summit of the curve, 
and with the factors determining the value of this ordi- 
nate we are at present concerned. 
Helmholtz showed that the induced current reaches 
its maximum intensity at the instant the spark ceases to 
pass. The abscissa AB, therefore, represents the time 
occupied by the spark. In a properly constructed ap- 
paratus AB will be constant. Helmholtz showed also 
that the value of the ordinate CB is approximately 
equal to > in which M is the mutual induction be- 
JM 
tween primary and secondary, / the intensity of the cur- 
rent through the primary, and L the inductance of the 
secondary. If the break were instantaneous, making 
AB zero, CB would equal the expression given above; 
it falls below that value more and more as AB increases, 
but so long as AB is constant the relation between the 
