THE INTERRUPTED HIGH-VOLTAGE PRIMARY,OR MIXED CURRENT.

BY

GEORGE J. ENGELMANN, M.D.,pF ST. LOUIS.

FROM

THE MEDICAL NEWS,

February 3, 1894.

[Reprinted from The Medical News, February 3, 1894.]

THE INTERRUPTED HIGH-VOLTAGE PRIMARY,OR MIXED, CURRENT.

GEORGE J. ENGELMANN, M.D.,OF ST. LOUIS.

The interrupted high-voltage primary or mixedcurrent is one of the results of experiment with mynew independent interrupter, devised for my faradicapparatus, but to be used also in connection withany galvanic and faradic apparatus; it has provedto possess an individuality peculiar to itself and ofgreat physiologic efficiency, so that I am convincedof its therapeutic value and present it for the con-sideration of the profession.

This current, which I term the interrupted high-voltage primary, or mixed, current, is obtained bythe interruption of the galvanic flow passing throughthe secondary coil of the faradic apparatus, and istaken from the terminals of that secondary coil,here used as a primary, which is of higher voltage,of many more winds and greater resistance thanthe ordinary primary in medical induction-instru-ments.

The current so obtained is hence not preciselyidentical with the primary faradic, and may prop-erly be termed a mixed current, if not an interruptedprimary of higher voltage.

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A well regulated, controllable interruptor is aboveall necessary. 1 Any galvanic battery may be used ;

one pole is connected with the interruptor, andthrough this to one of the terminals of the secondarycoil of the faradic apparatus 2 (the binding-postfrom which the secondary current is taken) ; the

B. Galvanic battery. I. Interrupter. s.C. Secondary coil-— X and -)-X. Terminals of coil. C. Core and primary coil.E. E. Electrodes.

1 For slow interruption, simple muscle-stimulation and mas-sage, the interrupter ordinarily connected with a complete gal-vanic apparatus may be used, or, for rapid interruption, a com-mutator attached to the shaft of a motor, but precision is neces-sary, and ere long the perfected instrument, which has beendevised and constructed by Messrs. Waite & Bartlett in accord-ance with my suggestions, will be in the hands of the profession,and accurate work, record, and comparison of results will thenbe possible.

2 Not every faradic apparatus will answer, as most instrumentshave but a single coil and this may give a very unsatisfactorymixed current. To obtain the various therapeutically serviceablephases of this current an induction-apparatus, with a graded setof coils, is necessary ; but if it has but one secondary coil itshould be of approximately 1800 W. and 13 ohms R., or ofabout 800 feet of 22 wire, as this develops the most generallyuseful form of the interrupted high-voltage current, the painlessmuscle-permeating current.

3other pole of the galvanic battery is connecteddirectly with theremaining terminal of the secondarycoil, and with these same two terminals the rheo-phores carrying the electrodes are connected.

A current so produced combines the characteristicsof the galvanic and the induction flow; it has thesame galvanometric quantity and the same chemiceffect as a simple galvanic current of the same in-tensity, or, from the same number of cells applied inthe same manner plus the voltage and the physiologiceffects obtained from the winds of the coil; coiland patient being connected in multiple, the resist-ance is diminished and the current increased, butincreased in voltage rather than amperage—con-verted, I may say.

The physiologic effects are peculiar, and differmaterially from those of any other form of elec-tricity in medical use, the current combining, as itwere, the quantity and chemic effect of the gal-vanic with the voltage of the faradic; the effectsresemble most nearly those of the primary faradic,but are more powerful and indicative of greaterquantity, most marked in their action upon muscu-lar fiber, which is affected by this as by no other

form of electricity.A variety of effects are produced by the use of

different current-intensities and different coils; yetwhile this current will undoubtedly be of distinctvalue in certain nerve-lesions, it will prove pre-eminently a muscle-current, as it contracts themuscle most perfectly, acting upon every fiber inthe most marked manner, like a powerful interstitialor intercellular massage,

4The character and effect of the current depend

upon the following elements, which must be noted,as it is by a variation in these factors that the varyingtherapeutic results are obtained :

i. The number of cells or intensity of the primarybattery-flow.

2. The resistance and number of winds of (thesecondary) coil.

3, The number of interruptions.4, The position of the secondary coil in reference

to the core and primary.5. The character and location of the electrodes.1. The number of cells used or the intensity of the

primary battery-flow determines the galvatiometricmeasure and chemic effect; these being the sameas from an ordinary galvanic current without inser-tion of the coil and applied in the same manner, itis evident that the character of the current must ina measure depend upon this factor ; but as voltageand induction-effects are prominent, the number ofcells to be employed is determined, not by thechemic effect to be produced, but by the coil to beused. Only one cell can be employed in connec-tion with a short coil, the number of cells beingincreased with the resistance and number of winds inthe coil; but more than ten or twelve cells, if ingood condition, can hardly be used to good advan-tage, even with the long fine coils, at least onhealthy tissues.

2. It is the coil preeminently which determines thecharacter and effect of the current, 1 theresistance and

1 In speaking of the coil, I invariably refer to the secondarycoil of the faradic apparatus, in position on the instrument, usedas a primary in this circuit.

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number of winds materially varying its physiologicvalue, but not in precisely the same manner aswhen used as a secondary in the faradic currentproper. The faradic current from a coil of highvoltage, or many winds, has least quantity, whilstthe mixed current from this coil is of necessity oneof greatest quantity.

The lower the resistance of the coil and the lessthe number of winds, the more powerful the induc-tion-effect and the less the quantity of the primarygalvanic force to be employed : No. I coil (Engel-mann), 0.8 ohms R., 528 winds, has an effect, bothmotor and sensory, too powerful for therapeuticuse, even with one single cell of the weakest Le-clanche.

No. 11, the medium coil, 13 ohms R., 1750winds, with one cell from any galvanic battery,produces the most satisfactory, deep, muscle-con-tracting currents, permeating every fiber. This is,par excellence, the coil which gives value to the cur-rent, and it is remarkable how completely it can beconfined to a distinct muscle by the location of the

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electrodes; whilst permeating its fibers it does notseem to radiate beyond.

For the developing of the most satisfactory re-sults, the number of cells used must be increasedwith the resistance and number of winds in the coil:

Number of cellsFeet. Wire. Winds. found

to be effective.For a coil of 1500 36 4.000 4 to s

7.000 7“ 3°°° 36“ 4S°° 3 6 10,000 9 to 11

By longer coils muscular contractions are likewiseproduced; but these are more painful, and thechemic effects of the galvanic current begin toassume prominence; these should prove efficientfor other therapeutic purposes, when more markedgalvanic effects are called for.

3. Change of relation between the secondary coiland the primary coil and core, /.<?., the moving toand fro of the coil on the scaled slide, varies the in-tensity of physiologic effect. This variation ofintensity is similar to that of the primary faradic,but differs in some features; if coils of low electro-motor force are used, the intensity of physiologiceffect is increased by a sliding out of the coil awayfrom the core ; this is most marked in the coil offewest winds, coil I, 528 winds; somewhat less so,but still very decided, in coil 11, 1750 winds,13 ohms R. ; coils of higher E. M. F., longer;fine-wire coils, on the contrary, weaken the current-effect by the drawing out of the coil, or the movingaway from the core; this is true, even of the coilof 1500 feet, or 4000 winds, and of the muscle-coil

7of fine wire in multiple, 6500 winds, and only4 ohms R.

The true primary coil of the apparatus is ignoredin these experiments, and its terminals are not con-nected. When this is done it acts as a damper, likethe copper tube of Duchesne, to weaken the cur-rent.

4. The number of interruptions, or the rates ofvibration, control the physiologic effect of this cur-rent, as they do that of the faradic, whilst thecheraic and galvanometric action is affected butlittle and that in a contrary sense.

Interruption and alternation affect the physiologicaction of this current in the same manner, but Ishall speak only of interruption, pure and simple,as it is the interrupted primary which will proveof greatest therapeutic value, this being more agree-able, less painful and harsh than the alternating,and equally, if not more, efficacious as a muscle-contractor, so that the alternating primary will onlybe used when it is of importance that all chemicaction be avoided. Both currents, interrupted andalternating, will respond to certain therapeuticindications; but as a simple muscle-contractor themore irritating and disagreeable alternating willfind little favor as compared with the interruptedcurrent; both, however, respond in precisely thesame way, as regards physiologic effect, to variationin the rate of interruption.

Other conditions being equal, the same numberof interruptions and alternations produce the sameeffect, i. e., 10,000 interruptions have the same com-parative effect as 20,000 alternations upon the cur-

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rent. As in the secondary faradic, the effect of thecurrent increases with the rapidity of interruptionfrom i to 2500 or 3000 per minute, and, afterattaining a maximum effect, decreases with increasedrapidity of interruption until a rapidity is reachedwith which all sensation ceases. Though the gal vano-raetric effect is unchanged, the chemic effect in-creases ; the more intense the current the greater thenumber of interruptions necessary to completelyannul its effect.

Coil I, heavy, with one cell, causes powerful andpainful contractions, too violent for general usewith the ordinary rate of interruption; yet it ceasesto have any effect, or to be felt, with 14,000 inter-ruptions per minute (this when full in, over core,with small sponge electrodes to upper and lowerarm, the effect depending greatly upon the moistureof the electrodes and the pressure upon them).

The 10,000-wind coil, 4500 feet of 36 wire, 11

cells, sponge electrodes to upper and lower arms,ceases to be felt at 25,000, whilst if only 7 cellsare used, the same result is accomplished by 20,000interruptions per minute.

The general law mentioned, of increase ofeffect with increase in rapidity of interruption, thendecrease with still greater rapidity, holds good withone curious exception, true of the secondary faradic,as it is of the interrupted, or alternating high-voltage primary; and this interesting phenomenon,which merits a more thorough discussion elsewhere,I must here at least note : it is that currents fromcertain coils, as far as I have observed, from 5000to 10,000 winds, 36 wire, under certain conditions,

9after passing that rapidity of interruption at whichthey cease to be felt, reappear with greater rapidity,again attain the previous maximum, to again loseall effect with still greater frequency of interrup-tion. In place of the simple rise and fall, there isa second shorter and additional curve of rapid riseto the previous maximum and fall to zero.

The 36-wire coil of 10,000 winds, with n-cellprimary galvanic force, ceases to be felt with 25,000interruptions, then reappears, regains its previousefficiency at 30,000, and again weakens as theinterruptions grow more rapid, to completely fadeaway as they attain a speed of 40,000 per minute;if fewer cells are used with the same coil, preciselythe same phenomenon is observed, the same effectsbeing produced by lower rates of interruption asthe current is weaker.

5. That the character of the electrode, whichdetermines penetration and surface-resistance, influ-ences this current, as it does both galvanic andfaradic, need hardly be mentioned ; material, size,degree of moisture, location, and pressure uponthe electrode, all serve to vary the sensation andeffect of the current, and must be considered asdetermining factors.

This interrupted, high-voltage primary currentpossesses an individuality which must secure it adistinct place as a therapeutic agent; by blendingthe quantity and chemic action of the galvanicwith the voltage and mechanical effects of the faradicwe are enabled to produce peculiar effects; yetboth are so modified that the resultant differs froma simple combination of these two forms of elec-

tricity. It differs from the painful interrupted oralternating galvanic as it does from the ordinaryfaradic, the secondary or induced current, and itwill be resorted to when deep, penetrating effectsare desired and when permeating muscle-currentsare indicated ; it will act, I believe, in those casesin which faradization fails. No other current, withsuch penetrating power, can be so localized andgrasp every fiber of a muscle as does this.

Therapeutic effects I have not, as yet, been ableto test, and cannot speak of its action uponmuscle in central and peripheral lesions, but phys-iologic experiment indicates the powerful influenceof this current, from proper coils, upon contractiletissue, and it is in this direction that investigationmust first proceed.

In conclusion, a word of caution to the operator:Care must be exercised in the selection of battery-force and coils until a knowledge of the currentand its effects is obtained. It is best to begin withthe use of the lowest current-intensities, or thefewest galvanic cells which will take effect throughthe coil employed, or to use the number of cellshere indicated as suitable for the various coils,varying the current by the pushing in or out of thecoil, as the case may demand; when familiarity withthe current has been acquired, this maybe varied byvariation in the galvanic flow for certain effects. Itmust be remembered that coils of low E. M. F.,heavy coils of few winds, must be drawn out to in-crease the physiologic effect, whilst coils of higherE. M. F., the long, fine coils, vary less and in a dif-ferent manner; these weaken by drawing out. It is

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also important to remember that the current-effectincreases more distinctly than that of the faradic,with increase in the rapidity of interruption up to3000 per minute, and, after attaining a maximum,gradually decreases with increased rapidity, de-creasing in proportion to the current-intensity; thestronger the current the greater the number ofinterruptions necessary to reduce it.

A note must be made of the peculiar effect offine-wire coils of from 5000 to 10,000 winds, whichagain attain a brief maximum intensity with increaseof interruption after having been obliterated by acertain rapidity.

It is evident that this current is one easily ob-tained if a proper interrupter and a coil of suita-ble construction are available, as a single galvaniccell, Leclanche, Gonda, dry or red acid, will answerfor use with the muscle-coil, the galvanic battery,or a larger number of cells, being needed onlywith the longer coils, which are not as generallyuseful.

I trust that an earnest trial will be given theinterrupted high-voltage primary, which merits aplace in our therapy, if only for its permeatingmuscle-effects, and I am convinced that therapeuticuse will soon demonstrate the greater range of thisefficient current.

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