THE MEASUREMENT OF BREAK SHOCKS 35 
true value of CB and the value -> which it approxi- 
JLi 
mates, does not vary. 
We may use the expression -> therefore, as a physi- 
Lt 
cal basis for the measurement of break shocks, although 
we must note that the expression will not serve fully, 
since the factor of secondary resistance is not included 
in it, nor is there any factor for the influence of the 
manner of applying the stimulating electrodes. More- 
over, the expression is proportional to the strength of 
the stimulus only so long as the circuit is broken uni- 
formly. The expression serves in our quantitative 
scheme, therefore, only as a starting point. Its use even 
so far is justifiable only if physiological tests confirm the 
applicability of the physical relationships. That they 
do so completely will be shown in due course. 
Our next step is a consideration of the individual 
MI 
factors in the expression and a discussion of the 
Li 
means whereby they are to be determined. 
Of the three factors which make up the expression, 
one, /, the intensity of the primary current, is an easily 
measured electrical quantity, and is best determined 
directly by means of an ammeter in the primary circuit. 
The other two, M and L, are functions of the construc- 
tion of the inductorium, either by itself or as modified 
