966 MESSES. A. WALLEE AND A. DE WATTEVILLE ON THE INFLUENCE 
was increased or diminished, for the amplitude of the record does not increase 
proportionally with the strength of contraction. 
The greater number of our experiments were made on the peroneal nerve close to 
the tendon of the biceps, or at the head of the fibula, and all the accompanying 
figures were taken from the anterior tibial group of muscles. We, however, obtained 
similar results on other nerves, and with other groups of muscles, viz.: by stimulation 
of the supra-clavicular nerves, and of the median and ulnar nerves, using the muscles 
of the fore-arm as the indicator of effects. The experiments were made on ourselves. 
I. Polar Alterations of Excitability tested by Induction Currents. 
Preliminary .—Before using induction currents to judge of alterations effected by 
the galvanic current, we examined the effects of long series of induction breaks and 
makes. Our experiments gave the following results :— 
1. The height of successive contractions by make or break induction currents 
approaches more and more gradually to a maximum. The figures show a marked 
and progressive increase, similar to the “ stair-case ” increase obtained with repeated 
excitations of the ventricle apex (Tracing 12). 
2. The stronger the excitations the more rapid is the initial increase. 
We do not propose to discuss these points here, but only record them in evidence of 
an alteration effected by induction currents, which must not be attributed to the 
galvanic current when it coexists. Anticipating upon some remarks we shall have to 
make on ascending and descending series by makes and breaks of the galvanic current, 
we interpret the progressive ascent to signify progressively increasing excitability as 
an after-effect of each successive excitation. We also observe that the ascent is more 
marked with the kathode than with the anode. 
Electrical connexions were established as shown in Diagram II. 
