2 INDUCTION SHOCKS 
operates to make uncertain the attempts of investigators 
to duplicate the experiments of others. 
No one will question the desirability of being able to 
measure f aradic stiniuli, both for the sake of controlling 
the stimuli used iii pne's own experiments, and also in 
orrier 'tjiart ^these/'.s.tiniuli may be so described as to 
enable other workers to duplicate them as occasion 
arises. 
The purpose of this work is to outline a system for 
calibrating the apparatus used in generating induction 
shocks, so that the value of the shocks may be expressed 
in terms of stimulation units; these units to be appli- 
cable to any properly constructed induction apparatus, 
and to be based upon determinations which can be made 
in any ordinarily equipped physiological laboratory. 
The system proposed is not a new departure, but is an 
extension and amplification of previous systems. 
Historical. The phenomenon of electromagnetic in- 
duction was discovered by Faraday in 1831, and its 
physical characteristics were very thoroughly worked 
out by him and by Henry about the same time. The 
first suggestion for the physiological use of induction 
shocks appears to have been made by Sturgeon* hi 
1837, and from that time to the present their use in this 
connection has continued. 
Various forms of induction apparatus have been de- 
* Annales de Sturgeon: 1837, p. 477. 
