CHAPTER XII 
ERRORS TO BE AVOIDED 
INCIDENTAL results of the several years of study spent 
in developing the quantitative method here presented 
have been to emphasize the importance of certain pre- 
cautions, and also to reveal the errors committed by 
some users of induction shocks in their efforts to make 
quantitative comparisons by indirect methods. 
Probably the most urgent general precaution calling 
for discussion is that of maintaining good electrical con- 
tacts throughout. In a mechanism so complicated as 
that shown in Fig. 8 loose contacts which may easily 
escape observation are likely to render quantitative ob- 
servations completely valueless. The user of the appa- 
ratus must keep continually in mind the importance of 
maintaining tight contacts, and by frequent inspection 
must assure himself that they are so. The sliding con- 
tacts provided for the secondary coils in some forms of 
inductoria are very untrustworthy and should not be 
used if fixed ones are available. 
In applying stimulating electrodes one must have in 
mind that the induced current stimulates at the cathode, 
and must know which electrode this is. A simple 
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