974 MESSES. A. WALLEE AND A. DE WATTEVILLE ON THE INFLUENCE 
strength of galvanic current that a given tetanus is greatly increased, or that pre¬ 
viously ineffectual stimuli tetanise when a galvanic current traverses the coil in the 
same direction as that of the break induction current; and, conversely, that a tetanus 
is greatly weakened or abolished when a galvanic current traverses the coil and body 
in the opposite direction to that of the break induction current. With the two cur¬ 
rents in the same direction, all induction kathodes in the body coincide with galvanic 
kathodes, and the increased effect is katelectrotonic ; with the two currents in opposite 
directions, all induction kathodes in the body coincide with galvanic anodes, and the 
diminished effect is anelectrotonic. The latter statement is proved by showing that 
the interference is physiological, inasmuch as the time which elapses between the 
removal of the galvanic current and the contraction produced by the released faradic 
excitation is greater than a make latency, and may be as long as a break latency. 
From this it is a legitimate inference that the former statement is also true 
(Tracing 25). 
II. Polar Alterations of Excitability during the passage of a Galvanic 
Current tested by makes and breaks of a Galvanic Current. 
Preliminary .—Before using the make and break of a galvanic current as the test 
of alterations during and after the passage of an uninterrupted galvanic current in the 
same circuit, we examined the series of effects of the former alone. As was to be 
expected, this test showed more marked variations than had been found with induc¬ 
tion currents. The full discussion of the alterations with time and current strength of 
the excitability during and after galvanisation demands however prolonged investiga¬ 
tion, and will form the subject of a separate paper. We shall only anticipate upon 
that part of the question sufficiently to justify certain statements. 
We observe that a horizontal series of make contractions, with equal duration and 
interval of current, can be converted into an ascending series by using a stronger cur¬ 
rent, or by altering the excitation rhythm to one of short duration and long intervals; 
that, conversely, a horizontal series can be converted into a descending series by using 
a weaker current, or by altering the excitation rhythm to one of long duration and 
short interval. 
We shall show, when we come to treat of the after-effects, that excitability after 
kathodal polarisation is at first diminished, subsequently increased (Tracings 8, 34). 
We also borrow an observation from a future paper on which we base the statement 
that this diminution of excitability increases in degree and in duration up to a certain 
limit of strength and duration of polarisation, and that beyond that limit it diminishes 
and sooner gives place to a more marked increase of excitability. Upon these data 
we base the statements that descending series indicate that each make excitation 
occurs during the period of diminished excitability consequent on previous make, 
and that ascending series^ indicate thaUeach t make excitation occurs during increased 
excitability consequent on previous make. 
