CHAPTER II 
FACTORS WHICH AFFECT THE STRENGTHS OF FARADIC 
STIMULI 
ANY scheme for measuring induction shocks, if it is 
to be wholly satisfactory, must take into account all 
the sources of possible variation present in the mechan- 
isms by which the shocks are generated and applied 
to tissues. The numerous methods which have been 
worked out hitherto have been uniformly based upon 
sound physical principles, and give accurate results so 
far as they go; they leave something to be desired, how- 
ever, in that none of them deals with all the conditions 
of variation which are actually present whenever tis- 
sues are stimulated, and their usefulness is limited by 
just that much. The justification for the present work 
lies in its attempt to take into account all the sources 
of variation which exist. These are to be divided into 
those whose influence upon the strength of stimuli is 
in accordance with mathematical laws, determinable by 
the experimenter, and those which are not apparently so 
determinable. The former are made the basis for the 
system of measuring stimuli herein described; the latter 
are studied with a view to showing how their effects 
may be minimized. 
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