CALIBRATION SCALE FOR BREAK SHOCKS 59 
yields at once data for computing r By averaging 
several experiments this part of the field can be cali- 
brated with sufficient accuracy. 
It must be stated, however, that in the innermost 
part of the field, including about half of the length of 
the primary coil from zero outward, the calibration num- 
bers determined by the v. Fleischl method will be found 
to differ somewhat according as the tissue used as an 
indicator has high or low resistance, high resistances 
showing larger calibration numbers than low ones. For 
this reason it is desirable to avoid using this region in 
work which requires a high degree of accuracy, unless 
a calibration has been previously worked out for the 
resistance actually to be employed. Experience shows 
that occasions when it is necessary to use the first 5 or 
6 centimeters of the scale are of rare occurrence in most 
kinds of experimental work. 
