THE INDUCTION COIL;

ITS

Varieties and the Differential Indicationsfor their Use.

BY

A. D. ROCKWELL, A.M., M.D.NEWYORK.

/» * </•/

Reprinted from The Medical Record, November 8, 1884.

NEWYORK;

TROW’S PRINTING AND BOOKBINDING CO.201-213 East Twelfth Street.

i8

THE INDUCTION COIL:

ITS

Varieties and the Differential Indicationsfor their Use.

BY

A. D. ROCKWELL, A.M., M.D.,NEWYORK.

Reprintedfrom The Medical Record, November 8, 1884.

NEWYORK:TROW’S PRINTING AND BOOKBINDING CO.

201-213 East Twelfth Street.

ISB4.

THE INDUCTION COIL—ITS VARIETIES ANDTHE DIFFERENTIAL INDICATIONS

FOR THEIR USE. 1

When solicited to contribute something to the annualmeeting of this Academy along that line of research inwhich I have been interested for so long a time, I hesi-tated in the selection of a topic. Of material there isplenty, and of sufficient importance. The whole field ofthe physics, physiology, and therapeutics of electricitylies open before us. The comparative value of its threesubdivisions offers a subject for discussion and the rela-tion of experiences, while the differential indications forthe use of these various forms—galvanism, faradism, andfranklinism—is of still greater importance and even lessunderstood.

Vital in interest as are each and all of these themes,and others that occurred to my mind, they seemed to beexcluded from discussion here, since it has been sug-gested that whatever is presented should flavor some-what of originality, or at least be not altogether hack-neyed ; and these topics have, one and all, been dis-cussed at various times in the current medical literatureof the day, and are more or less fully considered in manyof the works devoted to electro-therapeutics. The laud-able aspiration of this Academy, then, as attested by theprospectus lately issued, confirms the aphorism that“ originality is a thing we constantly clamor for,” aswell as “constantly quarrel with.” Unfortunately, how-

1 Read before the annual meeting of the American Academy of Medicine, atBaltimore, October 28, 1884.

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ever, pure originality in thought or methods of expres-sion is the gift of but few. Old and long-forgotten ideasare being constantly rehabilitated and brought forwardunder the guise of new and advanced opinions. In thisway, much that would otherwise be lost or fall short ofits proper utilization becomes, through a more persistentand perhaps clearer presentation, a practical part of theworld’s integral store of knowledge. While, therefore,none of the facts in physics that I propose here to pre-sent are in any sense new, yet there has been no generalappreciation of them, and but little knowledge, evenamong those who have been endeavoring, in a blind sortof way, to utilize them, that such facts existed.

As to the few statements that are made along the lineof therapeutics, the most that I can say of them is thatthey are the result of much experience and of very manycarefully recorded observations, and if presented withany measure of clearness ought to be of some little ser-vice to those who are interested in but who have givenlittle thought to the matter. But to my theme. Thereare two kinds of electro-magnetic machines that are pre-sented to the medical men for therapeutic purposes. Thefirst is termed a separate coil, and the second a continu-ous or single coil apparatus. The separate coil appara-tus is the one most commonly used and the one mostgenerally understood. The separate coil is the varietydescribed and illustrated in every text-book of physics,but not in sufficient detail to make clear its mechanismwhen used for medical purposes. Craving the indul-gence of those who may be thoroughly informed on thesepoints, and who may therefore regard as primitive theremarks that follow, let me, bv the aid of the accompany-ing diagram (Fig. i), describe the course and influence ofthe electric current in an ordinary separate coil faradicapparatus.

All induction machines are composed of not less thantwo coils. The first or primary coil consists of a large,well-insulatedwire surrounding a bundle of soft iron wire,

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which forms a magnetic centre. Over this first or pri-mary coil is wound a coil composed of several convolu-tions of fine, well-insulated wire for the induced current.

Fie. T.

The terminals of the first or primary coils of wire areunited, one end to the battery that operates the coil, andthe other to the part of the automatic rheotome accord-

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ing to the following description. As the battery is theimportant factor, let us start from it and follow the con-nections and action of the combinations that produce theeffect:

The positive pole (P) of the battery is connected withthe governor marked A (Fig. i). The negative pole Nof the battery is connected with the first end of the pri-mary coil, while the last end of the primary coil is con-nected with the spring support B. The electro-motiveforce is conveyed from the battery through the primarycoil to the spring support B (rheotome), thence to theplatina-pointed screw of the governor D, and lastly to thebattery, making the complete circuit.

In the centre of the coil and surrounded by the softiron wires is placed a soft iron rod. One end of the rodis bent at right angles, so that the hammer on the springis directly over and can move toward this soft iron rod,marked C. When the vibrating spring is resting againstthe platina-pointed screw D and the battery is connectedwith the coil, the current, as it passes over the wire ofthis primary coil, renders magnetic both the centre bun-dle of soft iron wires and the soft iron rod.

The magnetism is of sufficient force to attract the softiron hammer on the spring, and draw it down or near tothe magnetized rod C.

This movement of the spring severs the connectionbetween the spring and the platina-pointed screw D andopens the circuit. The soft iron rod, therefore, loses itsmagnetism. The spring ceases to be held down, its ten-sion being sufficient to raise it to a horizontal position,where it again rests in direct contact with the platina-pointed screw D. Again the circuit is closed and theprocess as described is repeated with inconceivable rapid-ity. By the action of the battery current, as it is conveyedover the primary coil, and the influence of the magnet-ized bundle of soft iron wires, a current is induced uponthe second coil of fine wire which surrounds the primarycoil. This power of induction can be established to the

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fifth and sixth coil, and further if the magnetic field isproperly arranged.

In the ordinary form of induction coil just described,the terminals of the secondary or fine wire coil are freeand in no manner connected with the primary circuit.The influence of magnetism produces a current which wecall pure induced.

In the continuous coil apparatus, on the contrary, wenot only receive the inductive influence, but the primaryinfluence as well, since it is carried over in combinationwith the induced currents. Although called a continu-ous coil, it is really made up of several distinct coils, andeach successive coil increases in length but decreases inthickness. These coils are wound over each other, andare tapped at different portions of their length, but, un-like other forms, they make direct connection with eachother. This accounts for an apparent contradiction ofterms that might prove confusing.

These coils (Fig. 2) are, for convenience ofillustration,represented by the upper straight lines I, 11, 111, IV,termed, respectively, the primary, first, second, andthird induction coils. The letters A, B, C, D, E rep-resent the different posts of the continuous coil appara-tus to which the conducting cords are attached, whilethe numerals 1, 2, 3, 4, etc., indicate the combinationsby which are obtained ten different qualities of current.The short line marked x, starting from A, represents thecurrent from the short, thick, primary coil marked I.Second line (2), current from the primary and first (I,II)induction coils combined. Third line (3), current fromthe primary and first and second (I, 11, III) inductioncoils. Fourth line (4), current from primary, first, sec-ond, and third (I, 11, 111, IV) induction coils. Fifthline (5), current from the first (II) induction coil only.Sixth line (6), current from the first and second (11, III)induction coils. Seventh line (7), current from the first,second, and third (11, 111, IV) induction coils. Eighthline (8), current from the second (HI) induction coil.

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Ninth line (9), current from the secondand third (111, IV) induction coils com-bined. Tenth line (10), current fromthe third (IV) induction coil only.

Therapeutical considerations.—Whenwe consider the many combinations thatare possible in the continuous coil ap-paratus and the different qualities of cur-rent that result therefrom, its generalsuperiority over the separate coil is suf-ficiently evident; and this superiority be-comes more marked if we examine intothe varied physical and physiologicaleffects produced by these combinations.

Our object of inquiry, however, is notas to the relative merits of differentmachines, but as to the comparativevalue of and the differential indicationsfor the use of the various combinationsof the continuous coil apparatus. Thispoint of inquiry, although less importantthan when it relates to the two forms ofdynamic electricity, is yet of no littleaccount, and in some respects has beenfound to be more difficult of solution.

Fig.2.

Notwithstanding the many qualities ofcurrent that are derived from the con-tinuous coil, I have, after much observa-tion, reduced to three the number ofcombinations that seem to be worthy ofdifferential consideration.

Every therapeutic result that can beobtained by any of the ten combinationsheretofore considered, will in all proba-bility result from the use of some one ofthe following :

i. The current from the primary coil asrepresented by the line marked i (Fig. 2).

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2. The current from the primary and the first and sec-ond induction coils in combination, as represented bythe line marked 3.

3. The current from the primary and the first, second,and third induction coils in combination, as representedby the line marked 4.

The primary coil yields a current of large quantity butof small tension, owing to the fact that the wire of whichthe coil is composed is short and thick. It is worthy ofnote, however, that this current has considerable chemi-cal power. It will burn iron or steel, giving forth abright deflagrating spark, and will readily electro-plate,an effect not obtainable with any of the induction coils,either alone or in combination with each other. Thiscurrent is apparently very weak, and induces but slightmuscular contractions in the healthy person. In occa-sional pathological conditions, however, this mild currentacts with unexpected energy, producing muscular con-tractions far exceeding in vigor those that are calledforth by the stronger action of the induction coils.

On account of its mild but efficient action the currentfrom the primary coil is preferable for applications to thehead and the more sensitive portions of the body, and itwill, as a rule, relieve pains of a true neuralgic character,and especially when great tenderness exists along thecourse of the nerve, far more effectually than the cur-rent from any of the induction coils. It is impossible toaccount for this frequently observed fact, without it beascribed to a combination of the battery and the induc-tive influence. When dealing with an agent so subtleand so little understood as electricity, it is difficult to ex-press one’s meaning in terms altogether satisfactory, butthat such a combination is active and effective is evi-denced by the readiness with which electrolytic effectsare produced. Asthenopia is a symptom that I haveknown to be greatly relieved and even cured many timesby electricity, but more especially through the use ofthe primary coil. The tired, aching eye is both tempo-

rarily rested after each sitting and permanently strength-ened by continued treatment. There seems to be littleappreciation, either among ophthalmologists or generalpractitioners, of the great relief that may follow this treat-ment in the many cases where the eyes ache severely,if used even for a little time before breakfast or at twi-light, or where neuralgic pains exist in or near the eye,or where there is annoyance from muscse volitantes.

As we include in the circuit with the primary the vari-ous induction coils, the current increases in strengthwith each coil that is added. With the addition of thefirst induction coil a much greater strength is apparent,but the combination has no marked physical or physio-logical effects that need detain us. By including alsothe second induction coil in the circuit, however (linemarked 3, Fig. 2), we obtain a current of a peculiar andunique quality. Like the primary coil, it will electro-plate, but unlike it, it will not burn steel or iron. Thepeculiarity of this combination of the coils is that themaximum of power to contract muscular tissue is hereobtained. Each additional coil now that is attachedsimply gives a decreasing contractile power. Why themaximum of current strength is reached in the combina-tion of the primary with the first and second inductioncoils it is difficult to say, excepting as we ascribe it tothe law of harmony or polarization that is brought aboutby properly conditioning the magnetic centre of thehelix, the several coils composing the helix, and the bat-tery influence acting upon the coils. The current fromthis combination is not at all pleasant; it is keen andcutting in character, and with its strong contractile prop-erties it is peculiarly adapted to those cases where pow-erful impressions are called for. Hence in not a fewcases of paralysis where the response to galvanism isperfect, but where there is a diminution of farado-mus-cular contractility, I have found it preferable to any ofthe other qualities of current to be derived from the con-tinuous coil apparatus.

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In superficial forms of anaesthesia it is, perhaps, in noway superior, but in certain persistent and more deeplyseated forms of lost or perverted sensibility it is decid-edly more efficacious than other combinations. Itsgreater contractile power over muscular tissue, both vol-untary and involuntary, renders it more efficacious incases of menstrual suppression, and also for atrophiedconditions of the uterus, for which so much has beendone by electrical methods of treatment. In cases ofdysmenorrhoea, as well as in the various neuralgias, myexperience leads me to exclude its use. Faradism hasbeen used, and with success, to destroy the foetus in ex-tra-uterine pregnancy. While I greatly prefer the gal-vanic current, having always used it without the slightestill effect, yet if the faradic is employed 1 should not re-commend the current from the coils now under consid-eration, but the one presently to be described ; for withthis latter form we obtain effects equally destructive tothe foetal life and with less violence to the contractiletissues of the mother. There are several other differen-tial points connected with the use of this series whichsuggest themselves, but they are of minor importance.

One other condition, however, deserves mention.Impaired virility is a defect for which relief is very oftensought. Its influence upon the mind is most unfortu-nate, and it should be understood that electricity is oftenof very considerable benefit in these cases. It is suffi-cient to say that no case which is in any way hopefulshould be abandoned until the current from the primaryand first and second induction have been tried.

When we include in the circuit not only the primaryand the fijst and second, but also the third inductioncoil as represented by the line marked 4, effects are ob-tained more interesting and satisfactory than from any ofthe other combinations.

These effects are pre-eminently tonic and sedative incharacter, and give for this quality of current a range ofusefulness wider than can be ascribed to the others.

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There are but few, in all probability, who at this day areunfamiliar with the term general faradization, and whodo not understand that by it is meant the application ofthe faradic current to the entire surface of the body,from the crown of the head to the soles of the feet. It isin the operation of general faradization, when we desireto obtain the best constitutional tonic effect that elec-tricity is capable of giving, that we resort to this com-bination of the primary and induction coils. Its actionon the motor and sentient nerves is less severe, and itsgeneral effects far more agreeable. For the relief of thatgreat army of symptoms that are so familiar and so per-plexing to those who have had much to do with neuras-thenic cases, there is, according to my experience, noth-ing to be compared with it. Even the galvanic currentby the method of central galvanization, so important inits direct effect upon the central nervous system, fallsshort of the therapeutic results that follow well-directedapplications of general faradization. When persistentfailure follows endeavors along this line of electrization,the cause of failure must be ascribed to hasty and faultymethods of administration. In no department of thera-peutics is it of more importance to be thorough in detail.He only will achieve the best results who appreciatesthis fact, who is willing to inform himself as to the modusoperandi of the methods, and who will devote in indi-vidual cases a reasonable degree of time and patience incarrying them out.