THE APPLICATION OF THE ELECTRIC LIGHT CURRENT 
IN ELECTRO-THERAPEUSIS. 
BY CHARLES JEWETT, A. M., M. D. 
Read before the Brooklyn Gynecological Society, April 7, 1892. 
Electrical effects in therapeutics, as elsewhere, depend mainly 
upon the current-strength or volume of the circulating force. 
This in turn depends upon the electro-motive force, or the 
pressure under which the current moves, and the resistance, 
or the obstruction which opposes the passage of the force through 
the medium in which it circulates. A clear conception of the sig- 
nificance of these terms affords the key to a practical knowledge 
of electro-physics. Since, in the adaptation of the electric light 
current to office use, the doctor must be to a great extent his 
own electrician, a few words in elucidation of these rudimentary 
facts of electrical physics may not be amiss before taking up 
methods and appliances for our purpose. 
ELECTRO-MOTIVE FORCE. 
The electro-motive force of a current of electricity is the pro- 
pelling’ power of the current. To borrow an illustration from 
mechanics, electro-motive force is to an electrical current what the 
driving force or pressure is to a current of water. As water tends 
to flow from a higher to a lower level, so electricity tends to move 
from higher to lower tension, in other words, to seek an electrical 
level. Just as the; force of a waterfall is measured by the difference 
of water level above and below the fall, so the pressure of 
an electrical current is proportionate to the difference of electrical 
level or potential, in the body from which and that to which the 
current is due. Electro-motive force then depends on difference of 
electrical level or potential. It is frequently spoken of, therefore, 
as the difference of potential, or simply the potential. The term 
tension is also used synonymously with electro-motive force. 
Definite units have been adopted for the measurement of 
each of the factors of electrical currents. The unit of electro- 
motive force is the volt. The potential or pressure of the current is, 
therefore, sometimes termed the voltage. The value of a volt is 
approximately the electro-motive force of a single Daniell cell in 2 
perfect working order. More definitely, it is the equivalent of a 
mechanical force capable of generating a velocity of one metre per 
second in a mass of one gramme. 
CHARLES JEWETT, A.A/., M.D. 
ELECTRICAL RESISTANCE. 
A column of water moving through a conducting pipe meets 
with a certain amount of resistance. So the circulation of elec- 
tricity encounters more or less obstruction from the conducting 
medium in which it moves. This is termed electrical resistance. 
It varies with the nature of the conducting medium. It is least in 
metals which are consequently good conductors. In many sub- 
stances, such as glass, hard rubber and dry wood the resistance is 
so great that these bodies are practically non-conductors. Again, 
electrical resistance, like that of the water column, will vary directly 
as the length of the conductor and inversely as its cross section. Long 
wires, then, will offer proportionately more resistance than short 
ones of the same size and material, and fine wires more than coarse 
ones in the exact ratio of their sectional areas, and the same is true 
of all conducting media. 
It must be borne in mind that in battery circuits the battery 
forms a part of the circuit, and the battery elements as well as the 
conducting wire offer resistance. The resistance within the battery 
is called the internal resistance in distinction from that without 
which is the external resistance of the circuit. The internal resist- 
ance varies greatly in different types of battery, and this fact has 
an important bearing in explaining the great difference in the 
performance of batteries of different construction. 
The unit of resistance is the ohm, the value of an ohm being the 
resistance of a column of pure mercury whose cross-section is one 
square millimetre, length 106.25 cm., and the temperature zero 
centigrade (the temperature of melting ice). 
CURRENT. 
The term current technically stands for the current-strength, 
or the volume of electricity that flows in the circuit. The 
current-strength depends upon the resistance in the circuit and 
the electro-motive pressure under which the current is impelled. 
Remembering that the battery itself forms a part of the circuit, it is 
plain that a battery of high internal resistance, like most of those 
in common use, can yield but a limited volume of current, however 
small the resistance in the metallic or external portion of the 
circuit. On the other hand, storage batteries, in which the internal 
resistance is but a few thousandths of an ohm, yield current in THE APPLICATION OF THE ELECTRIC LIGHT CURRENT. 
3 
enormous volume through small external resistance. The same is 
true of all batteries of low internal resistance. Since the internal 
resistance of a battery is due chiefly to the resistance of the fluid 
between the plates, it follows that batteries of large plates are 
capable of yielding more current than batteries of the same type 
having small plates, since the conducting power of the fluid column 
varies directly as the area of its cross-section. But it must not be 
forgotten that the current volume from large cells is greater than 
from small ones of the same type only when the external resistance 
is small. Where high external resistances are concerned, like those 
of the human body, the size of the cell makes practically no differ- 
ence in the current-strength, as can readily be shown by Ohm’s 
formula. 
No matter what the volume of current a given battery is capable 
of yielding, the current which actually flows in the circuit will be 
limited by the external resistance. Resistance, however, is par- 
tially overcome by increased pressure, therefore whatever the ex- 
ternal resistance, so long as there is any current at all, its volume 
will become greater and greater in proportion as the electro-motive 
force is higher. The current, therefore, varies directly as the 
potential or electro-motive force under which it moves and inversely 
as the total resistance. This fact is known as Ohm’s law, and is ex- 
pressed mathematically by the formula C = E -j- R. It is evident from 
this formula that if the resistance were zero, the current would be 
infinitely great, even from a single cell of battery. If the resistance 
were infinitely great, the current would be zero, no matter how 
powerful the generator. It will be found in practice that the amount 
of resistance in the circuit is a very important factor in determining 
the volume of current. When the external resistance is reduced to 
an amount so small as to be inappreciable, when, in other words, 
the battery or dynamo is short-circuited, it yields its full volume 
of current. On the other hand, if the resistance is very great the 
current may be insignificant even from a generator of great power. 
The unit of current is the ampere, the value of which is the 
volume of current that flows in a circuit, under a potential of one 
volt through one ohm of resistance. In medicine, however, where 
we have to do with small quantities only, the mitliampere or 
thousandth of an ampere is the unit commonly employed. 
We are now prepared to understand the difference between 
battery currents and the current of the Edison light system. 
Currents from batteries of the ordinary type are currents of small 
volume, owing in part to the high internal resistance of these 
batteries. Moreover, since only about fifty elements are ordinarily 4 
CHARLES JEIVETT, A.M., M.D. 
used, the voltage is lower than that of the incandescent light 
current, and the drop in current-strength under high external resist- 
ance is greater. A battery of fifty of the latest pattern of Law 
cells, for example, in good order, is capable of giving on short 
circuit a current of about four amperes, with a voltage of 74. 
The Edison current, on the other hand, has a voltage of 115, and 
will yield a current, therefore, of 115 amperes, through a resistance 
of one ohm. 
Two terms, multiple arc and series, here require explanation. 
Instruments are said to be arranged in series when they are so con- 
nected in circuit that the current runs through them successively, as 
in Fig. 1. An instrument is in series when it is placed in one side 
of the circuit. Instruments are said to be arranged in multiple arc 
Fig. i. 
Fig. 2. 
when two or more are so connected as to form bridges or arcs 
between the two sides of the circuit. This latter arrangement is 
shown in Fig. 2. 
The ordinary applications of electricity in a doctor’s office fall 
under three heads: galvanism, faradism, cautery. Each requires 
a somewhat different adaptation of the incandescent current, which 
we will now proceed to consider. 
Galvanism. This I assume, and not electrolysis, is the proper 
term for the application of the smooth or interrupted galvanic 
current as used in gynaecology and in general medicine. It will 
naturally be feared that more or less danger may attach to the use 
of therapeutic currents from so powerful a source as the Edison 
dynamos. There is no difficulty, however, in using the direct THE APPLICATION OF THE ELECTRIC LIGHT CURRENT. 
5 
current from the Edison mains with entire safety. The whole 
secret lies in the use of plenty of resistance. The volume of current 
which flows into the office is limited first by the size of the con 
ducting wire. Again, at the point where the circuit enters the 
house, safety fuses of limited capacity are intercalated in both 
sides of the circuit. These fuses, which consist of thin lead or 
copper wire, act as safety valves, since they melt or “blow out” 
and break the circuit if the current by any accident exceeds the 
capacity of the fuse, which may be fixed at any amount required 
by varying the size of the fuse-wire. If now the current thus con- 
trolled is passed through a 16 c.p. lamp, connected in series as 
shown in Fig. 3, the volume of current which flows through the 
lamp, and, therefore, in the entire loop in which the lamp is con- 
nected, is about one-half an ampere. The lamp acts as a water- 
S. F. Safety fuses at the Edison terminals; L. 16 c.p. lamp; M. milammeter; 
R. Rheostat or current regulator. 
Fig- 3- 
gate does in a water-main, with this important difference, how- 
ever, that if the lamp breaks the entire circuit is instantly arrested. 
A larger or smaller current may be had by_ substituting for the 16 
c.p. lamp another of higher or lower capacity. The half ampere 
current, however, is a good stock current from which to draw for 
most gynaecological and medical purposes. By means of a suitable 
rheostat this current can be controlled as the flow of water is by a 
tap, and may be varied from zero to any number of milliampercs 
required. 
On first undertaking the adaptation of the Edison current to 
office uses I shared the opinion of Dr. Piffard that the high voltage 
of the current from the street mains would render it more painful 
than the currents of lower pressure we have been accustomed to 6 
CHARLES JEWETT, AM., M.D. 
use. Further examination of the subject has convinced me of the 
error of this assumption. Electro-motive pressure has no influence 
except to overcome resistance. The physiological effects of a 
smooth current depend upon the volume and quantity of current. 
With a given amperage actually flowing through the tissues, the 
effects are the same whatever the electro motive pressure. The 
current does the work, the pressure pushes it through the tissues. 
Since these views are somewhat at variance with a commonly 
accepted opinion among medical writers, «I may say that they 
are endorsed by my friend, Prof. Robert Spice, of the Cooper 
Union, a physicist of recognized authority. 
Under the belief that the high voltage of the Edison current is 
painful, Piffard and others make use of a shunt circuit for the 
Fig. 4 
purpose of reducing the potential. This plan may be understood 
by referring to Fig. 4. 
L and L1 are lamps connected in series in the main circuit. A 
secondary loop is led from points of the main circuit on either side 
of the lamp L. The patient is placed in this secondary or shunt 
circuit, which also includes the milammeter and the regulator, 
and both lamps are turned on. This arrangement is not only 
unnecessary, but it does not even accomplish what it is supposed 
to do. On short circuit the voltage in the shunt drops more or less, 
and may be varied, according to the resistance in the shunting 
lamp, from three or four to seventy volts. With the patient in 
circuit, however, the voltage is practically the same for a given 
current whether the patient is in the direct or the shunt circuit. 
For determining the polarity of the electrodes the milammeter 
affords the most convenient method, provided the direction in THE APPLICATION OP THE ELECTRIC LIGHT CURRENT. 
7 
which the needle turns with an up-current has once been deter- 
mined. In most instruments the needle is deflected in the direction 
in which the current flows. If, therefore, in the arrangement 
shown in Fig. 3, the needle of the milammeter turns to the right, E is 
the positive, E1 the negative electrode. The polarity may also be 
determined by the electrolytic action of the current. If the copper 
terminals are dipped at a short distance apart in a glass of water 
and a half ampere current turned on, hydrogen bubbles will be 
given off at the negative pole, while no visible action occurs at the 
opposite pole. Or if platinum terminals be used and dipped in a 
solution of iodide of potassium, a brownish discoloration will be 
noted about the positive electrode from the liberation of iodine. 
Faradism. For Faradism a coil may be operated by a switch 
from the main circuit. The current required may best be obtained 
by a separate loop with a 16 or 32 c.p. lamp, connected in series. 
The milammeter should not be included in this circuit ; it is 
desirable that a rheostat should be, for regulation of the primary 
current. 
No little misapprehension obtains in regard to the construction 
required in Faradic apparatus. It is a common error to assume 
that galvanic, Faradic and Franklinic electricity are different kinds 
of force. They are, in fact, one and the same. The essential 
differences in their physical or physiological effects is due to differ- 
ence in the character of the currents. Galvanic currents as 
ordinarily used are smooth, continuous currents. Faradic currents 
are alternating currents. The peculiar effects of a Faradic current 
are mainly due to the fact that it is an interrupted current. The 
current from the secondary coil is at the same time an alternating 
current. Yet the impulses in one direction are so much feebler 
(about 13 times) than those in the other, that little importance can 
be attached to the alternating character of the Faradic current. 
The physiological effects, too, vary with .the rate of interruptions— 
the number of periods per second. While the current-strength on 
short circuit is very small, the drop, even under great resistance, 
is comparatively little owing to the high electro-motive pressure. 
There can be no important physical difference, then, between a 
Faradic current and a direct interrupted galvanic current of the 
same volume and tension and number of periods per second. The 
tension of secondary Faradic currents as commonly used in medi- 
cine I have estimated at from 50 to 100 volts or more, and the 
current, on short circuit, averages about a half milliampere, does 
not often exceed a milliampere. A current of this strength and 
tension obtained from the Edison mains by the interposition of 8 
CHARLES JEWETT\ A.A/., M.D. 
suitable resistance and with the use of an adjustable rheotome, would 
answer all the purposes of Faradic electricity. With a milammeter 
capable of registering fractions of a milliampfere, precision of 
measurement would be possible by this method, and that at 
present is out of the question with Faradic instruments. Having 
rheostat, milammeter, rheotome and patient in circuit, the required 
current could be turned on and broken at the required rate of inter- 
ruption. With suitable metric apparatus the current-strength and 
the number of impulses per unit of time could always be accurately 
known and recorded. The Faradic coil, however, is practically in- 
dispensable as a simple and convenient source of interrupted 
currents of infinitesimal volume and high tension. Precision of 
measurement in the use of Faradistn is not yet possible. 
The requirements of a Faradic instrument may be met by a very 
simple construction. All that is needed is an induction apparatus 
with a secondary coil of long, fine wire and a rheotome or rheo- 
tomes adjustable to give from 2 to 200 interruptions per second. 
An instrument thus simple will accomplish all that is pos- 
sible with the multiple coils of Kngelmann and others. It is a 
fallacy to assume, as certain writers on this subject have done, that 
a secondary coil, wound with a given length and fineness of wire, 
ensures a current of fixed volume and tension, even with the same 
primary. Current-strength, as we have seen, depends upon the 
resistance in the circuit and the electro-motive force. Resistance 
varies with the moisture of the electrodes, their area and firmness of 
contact, the thickness and dryness of the skin at the point of con 
tact, and other conditions. Flectro-motive force, and therefore the 
current in the secondary circuit, varies with the strength of the 
primary current, the rate of interruptions, and the extent to which 
the outer covers the inner coil. Hence, an induction coil wound 
to give the highest electro-motive force that can be required for any 
use will answer for all uses. The tension, and therefore the current, 
can be graduated from this maximum to zero by moving the outer 
coil so as to gradually uncover the inner one. or by regulating the 
strength of the primary current by means of the current controller. 
A still simpler method of regulating the secondary current is by 
means of a current controller placed in the secondary cifcuit. The 
entire range of tension (and therefore volume) of which the coil is 
capable is thus at command without moving the outer coil or 
changing the strength of the primary current 
More or less importance is attached to the so-called primary 
current from induction apparatus by many writers on electro-thera- 
peutics. This current is nothing more than a series of impulses all THE APPLICATION OF THE ELECTRIC LIGHT CURRENT. 
9 
moving in one direction, and the result of self-induction in the 
primary coil. It has no properties that distinguish it in any 
essential particulars from induced currents obtainable from the 
necessary coil, or an interrupted direct current of equal volume 
and tension. 
Fig .5. 
The most approved Faradic apparatus is that constructed on 
the Du Bois-Reymond principle. An excellent Faradic instrument 
in point of both mechanical construction and physical perform- 
ance is made by the Law Battery Co., of New York, and is 
Fig. 6. 
shown in Fig. 5. Its secondary coil is wound with 1,200 feet 
of No. 32 wire, giving a wide range of tension, and it is provided 
with two rheotomes for slow and rapid interruptions. The outer 
coil is movable over the inner by means of a rack and pinion. 
Cautery. A convenient plan for cautery currents is shown 
in the right-hand section of Fig. 8. A is a bank of lamps 10 
CHARLES JEWETT\ A.M., M.D. 
arranged in parallel multiple-arc. Two of the lamps are 16 c.p. 
lamps, each carrying a little less than a half ampere (0.43 ampere)* 
Fig. 7. 
current. The others are 50 c.p. lamps, having each a current 
capacity of not quite one-and-a-half amperes (1.36 amperes). Each 
lamp turned on adds to the current an amount equal to its own 
capacity. Such a bank is suitable for a twenty ampere current, 
Fig. 8. 
which is an average cautery current. The system may be easily 
extended to give thirty or forty amperes for heavier work. If a 
♦Edison lamps. THE APPLICATION OF THE ELECTRIC LIGHT CURRENT. 
11 
switch-plug is placed in B, the right-hand section is ready for 
cautery; if in C, the left-hand section may be used for galvanism. 
The conducting wires in the handles of most cautery electrodes 
are made too light, and are liable to become heated. The contact 
points are especially apt to suffer, and for this reason it is well 
to close the contacts of the electrode handles permanently, and to 
make and break circuit by a heavy floor push-button such as is 
shown in Fig. 6. 
The simple plan above described will be found far more con- 
venient and satisfactory for cautery currents than the cumbersome 
Fig. 9. 
and costly motor-dynamo-transformer. The latter apparatus is 
wholly unnecessary for the purpose. 
For a portable cautery plant the storage battery has practically 
supplanted all others. A storage battery, however, to be kept in good 
condition must be used daily, must be recharged as often as used, 
and its charge must never be more than one-third exhausted. It is 
advisable, therefore, to make the portable storage battery do duty also 
for office purposes. Most of the annoyance which attaches to the 
use of storage batteries that require to be sent out at short intervals 
t<5 be recharged may be obviated when the charging current can be 12 
CHARLES JEWETT, A.M., M.D. 
had on tap in the office. If the battery is kept well charged, and 
the charging current allowed to run through it daily, very little 
additional attention will be needed to keep it at all times in perfect 
working order. For charging, the positive terminal of the charging 
wire must be connected with the positive pole of the battery, and 
the negative with the negative pole. Moreover, the volume of the 
charging current must be regulated according to the size or 
Fig. 10. 
capacity of the battery. It may be iust enough so that the fluid 
does not boil perceptibly. The battery will be injured or destroyed 
if these precautions are not observed. A safe charging rate is three 
ampferes for every square foot of anode surface in the battery 
plates. A more convenient rule, however, is about one amp&re for 
every twenty ampere-hours of battery capacity. For the usual 
medical battery a half ampfere current answers sufficiently well. A 
simple and economical method of charging is shown in Fig. 7. The 
battery is connected by a loop with a single 16 c.p. lamp circuit, THE APPLICATION OF THE ELECTRIC LIGHT CURRENT. 
13 
which is used for ordinary illumination. When the lamp is turned 
on the battery is being charged. Frequent charging and the main- 
tenance of a full charge are thus secured without special attention. 
A search-lamp may be operated by the storage battery or by con- 
necting it with the terminals of the cautery plant represented in the 
right-hand section of Fig. 8. The current required by the minia- 
ture lamps usually employed for this purpose is about two or two- 
and-a-half amperes. Turning on two of the 50 c.p. lamps in the 
bank the current may then be turned up by the regulator till the 
search-lamp burns to full incandescence. 
Rheostats or current regulators. After careful comparison of a 
number of rheostats, I have found nothing better for use with the 
Edison current than the Bailey water rheostat. In the old instru- 
ment, however, the aluminum wire should be replaced with plati- 
Fig. 11. 
num to prevent corrosion at the contacts. The new Bailey regulator 
(see Fig. 9), made by the Law Battery Co., of New York, is in many 
respects an improvement on the old one. A good dry rheostat for 
the purpose is the Willms. The Vetter regulator is suitable for use 
only with currents of half an ampere or less. Where currents of 
large volume are required, as for charging storage batteries, a 
single lamp of large capacity may be used. A still more con- 
venient regulator for large currents is a bank of lamps arranged in 
parallel multiple-arc, as shown in Fig. 8. 
Milammeters. The milammeters sold by most instrument 
makers are inaccurate, unreliable, and otherwise imperfect. Abso- 
lute accuracy of measurement, while not indispensable for medical 
use, is certainly desirable. The only accurate milammeter at 
present made is that of the Weston Electrical Instrument Company, 14 
CHARLES JEWETT,\ A.M., M.D. 
of Newark, N.J. The instruments of this company are universally 
recognized as standard Another advantage of the Weston meter 
is the fact that it is absolutely “dead beat"—in other words, the 
needle moves to the reading and stops instantly. Unfortunately 
this instrument is a costly one. The next best milammeters that I 
have tested are the Vetter and the New Barrett meters. 
For those who prefer to purchase a switch-board fully equipped 
for use with the electric illuminating current, a suitable apparatus 
may be had of the W. F. Ford Surgical Instrument Company, of 
New York. A switch-board sold by the McIntosh Battery & Optical 
Company, of Chicago, is shown in Fig. io. 
A simple and inexpensive adapter intended for use with galvanic 
and Faradic apparatus only is made by J. C. Vetter & Co., of New 
York. It is a lamp socket with connecting posts for conducting 
cords. It may be screwed into any lamp socket or wall receptacle. 
The apparatus is shown in Fig. 11.