On the Progress of Electro-therapeutics (1872)

With a description of galvanic instruments invented by the author,

J. N. Hearder, D.Sc., Ph.D., F.C.S., Medical Galvanist, Plymouth; Galvanist to the South Devon and East Cornwall Hospital; Lecturer on Experimental Physics.

(Read at Exeter, July, 1872.)

The object of the present paper is not to ask for electricity a recognition of any claims to be ranked amongst curative agents, nor to offer any apology for introducing it as a subject for the consideration of the Devon Association. The attention which it has for many years excited, and the increasing interest which has prompted the clever clinical lectures on the subject, and the animated discussions of still more recent date, fully establish the former, and supersede the necessity of the latter.

My object is to endeavour to throw into the fund of general experience a few facts and observations gathered in the course of nearly half a century’s devotion to the study of electrical science, and its collateral employment as a therapeutical agent throughout the same period.

Taking it for granted that my hearers are all familiar with the three forms under which electricity has been employed as a curative agent, namely, Franklynic or Static, Voltaic, and Faradaic or Electro-magnetic, I shall proceed at once to give a few of my own experiences, and notice some facts not generally alluded to by writers on Electro-pathology of the present day.

First, with regard to Franklynic Electricity. There was a time when this form of administering electricity was the only one, if we except the occasional use of the Cruikshank’s form of Voltaic Battery, available for electricians, and it was with this I first experimented in Electro-therapeutics. There were three principal modes of applying it: 1st, the Spark; 2nd, the Shock; 3rd, the Aura.

FIRST—THE SPARK.

The ordinary mode of administering the Spark was very defective; it was usually done by placing the patient on an insulated stool, and connecting him with the prime conductor of the machine. A brass ball held by the operator was then passed over the part of the body to be electrified outside the clothes, and a series of small pungent sparks, varying in strength according to their length, thus passed between the surface of the body and the brass ball through the clothes of the patient. If the clothes were damp, or composed of any material but silk or wool, these sparks could not be obtained, unless a flannel covering of some kind were laid over the portion of the dress through which it was necessary to draw the sparks.

To remedy this, instead of holding the brass ball in the hand, I contrived an interrupted director, by which I could vary the length and strength of Spark at pleasure, and obtain it through the clothes under all circumstances.*

* This instrument is described and figured in “Phylodanmonian” of June, 1830.

I do not think that the value of the therapeutic effect of the Spark has been sufficiently appreciated.

It had powerful rubifacient properties, and excited vascularity in the cutaneous tissues, and was extremely efficacious in exciting superficial circulation where languid.

In rheumatic affections it frequently acted rapidly and beneficially.

I observed almost invariably that after a general surface electrization, the action of the heart, as indicated by the number of pulsations, was reduced ten and fifteen per cent. Chilblains, sore throats, and asthmatic affections, yielded quickly to the influence of the Spark.

SECOND—THE SHOCK.

This knock-me-down process, under the usual mode of employing it, occasionally produced very serious mischief. The injudicious shocking of a joint to restore nervous energy after a dislocation often resulted in inflammatory action; but by reducing the strength of the Shock, and administering a rapid reiteration of very small ones instead of a few strong ones, the contrary effect was produced under corresponding pathological conditions.

For this reason I reduced my leyden jars gradually to small coated tubes, from which I could obtain small shocks in such rapid succession, as to be able to hold an individual as firmly fixed to a pair of brass handles as he often is now under the influence of the coil machine, and this long before coil machines were dreamt of. Precisely the same therapeutic effects were produced by this process as by the present one of Faradizing.

THIRD—THE AURA.

This valuable form has been almost entirely overlooked by chroniclers of electro-therapeutics.

The Association would scarcely credit the number of cases of inflamed eyes, and obstinate ulcers, and even of neuralgia, which were cured simply by throwing the Electrical Aura or breeze from a wooden or metal point upon the part affected.

The facts were numerous and indisputable, though the rationale was unknown.

Now, however, perhaps we should not be far wrong in ascribing them to the action of ozone, since we know that the Electrical Aura is one of the most fertile sources of its development.

This may be easily shown by a very simple experiment. If paper coated with a preparation of iodide of potassium and starch, commonly known as ozone test paper, be moistened and passed before an electrified point, a deep blue stain is instantly produced, and by moving the paper, the point may be made to trace blue characters upon it, as if written with a pencil.

At a Meeting of the Devon Association, held at Tavistock, I proposed that ozone developed from frictional electrical machines should be used in hospitals as an antiseptic or disinfectant; and I find that the same suggestions have not only been made by others, but apparatus have been contrived for developing it for this purpose from the Induction Coil.

INDUCED ELECTRICITY.

Deferring for the present any remarks on the early attempts to substitute Galvanism for frictional electricity as a therapeutical agent, I come at once to Faraday’s grand and very opportune discovery of the development of Static Electricity by the magnetic reaction of the Volta Electric Current, which gave a sudden impetus to electrical investigations in a new direction.

I believe I was one of the first to apply the discovery to the construction of what is now called the Induction Coil, and certainly the first in England to show the extraordinary statical effects capable of being developed in the secondary coil, from the magnetic re-action of an included iron core.

My large Induction Coil, and some of the investigations made with it, were laid before the Plymouth Institution in 1856, and the Society of Arts and the London Institution in 1857, and I had been previously honoured with prizes from the Royal Cornwall Polytechnic Society for this invention.

It was merely an extension of the principle upon which my medical coil was constructed.

Without reviewing the numerous forms of the medical coils now in use, I may be pardoned if I briefly remark on the almost universal absence of what appears to me a most important element in their construction, namely, the establishment of a unit of force, and an accurate and definite system of graduation, by which experimentalists may be able to compare notes with each other.

In the construction of my medical coil to which I have the honour to draw the Society’s attention, there are three important features, not, I believe, to be met with in any other Faradaic instrument.

1st. The electro-motive force of the battery and resistance of the coil are so exactly adjusted to each other, that a single small Smee’s Battery, with about four square inches of platinized silver immersed, produces a very high magnetic development in the core.

2nd. The employment of a strong spring interrupter, which can be made to vibrate some hundreds of times per second.

3rd. My double index principle of graduation.

I employ two indices – one moving over an arc giving from one to eight degrees of force; and the other, like the minute hand of a clock, passing over a second arc which subdivides these degrees into quarters, thus quadrupling the number of increments.

Each degree of force is obtained by a definite length of secondary coil.

The value of this machine in obstetric practice was recognised by Dr. Barnes, of London, at whose suggestion I introduced certain modifications so as to increase its compactness, and render it a suitable “Vade Mecum” for the medical and obstetric practitioner; and I have only to refer to the remarks contained in a lecture delivered by Dr. Barnes, reported in The Lancet of November 12th, 1854, to show how far I succeeded in accomplishing the object.

The late Dr. Marshall Hall welcomed this machine with most unbounded satisfaction, “since by its means”, he said, “electricians need no longer misunderstand each other by experimenting with apparatus which did not admit of comparison, but that they could now compare notes with the greatest accuracy”.

The following case illustrates the value of my index mode of graduation as a means of diagnosis and a measure of the difference in certain pathological conditions.

Dr. Marshall Hall knowing that I had frequent cases under treatment, asked me to take particular notice of the various strengths of current required to produce equal amounts of muscular contraction under different conditions of reflex sensitiveness, and to note the degrees indicated on my machine. This, he said, would enable him to compare his notes with mine. The results were that, as a general rule, where the reflex sensory functions alone were impaired, muscular contraction was excited with a much less amount of power than when the reflex functions were in a normal condition, probably arising from the involuntary controlling action which the sensory nerves may exert over the nerves of volition, thereby modifying the development of a force which, if uncontrolled, might have been considerably greater.

A labouring man fell from a horse and bruised his neck on the left side: the result was an entire paralysis of the sensory powers of the left arm, while the motor powers remained intact. He could do any work or hold any article as long as his attention was directed to it; but the moment his attention was diverted, the article would fall from his grasp. He could tie his neckerchief if he stood before a glass, but not else. On one occasion he chopped off a piece of one of his fingers, and on a second sawed off the top of another, without having been aware that he had done so until he saw the mischief. Placing him under Faradaic treatment, remarkable effects were observable. A current which produced a very slight action in the right or normal arm excited the other so violently that I unwittingly received two or three tremendous thumps from the sudden contractions.

The motions produced were beautifully true to the influence of each individual muscle as it was separately Faradized; and the contortions of the limb were such as could not possibly have been excited, either by the strongest Faradization which the patient could bear, or the most intense volition which he could exert in the normal limb.

I once noticed a similar effect on passing the Faradaic current down the back of a cholera patient in articulo mortis, and immediately after death.

After life was extinct the reflex curvature of the spine, under a current which would scarcely have been appreciable in health, was something marvellous, and very nearly caused the body to twist out of bed.

In the case of the Anoesthetic arm just described, it was easy to note the difference between the degrees of force necessary to produce equal muscular contractions in the normal and abnormal limb, and to watch the controlling influence which the gradual return of sensation produced over the involuntary contractions resulting from electrical influence.

Again, two limbs may differ widely in their sensational susceptibility to electrical impressions, and this instrument measures accurately the difference between them, and affords a precise mode of registering the progress of convalescence.

Before dismissing the subject of Induced Electricity, let me briefly refer to some vague notions which seem to be afloat respecting the nature of so-called primary currents; that is to say, currents obtained from a primary wire alone, without the addition of a secondary one. These notions arise from an ignorance of the fact that the currents obtained from primary coils are really secondary ones, and only differ from those obtained from the secondary coil proper in being limited to a given degree of strength, determined by the length of primary coil. They arise, not from the battery current which excites the magnetism in the core, but from the wave of electricity produced by the cessation of magnetic reaction at the moment when the circuit is broken.

Increase of power in a primary coil is obtained by the employment of a greater number of battery cells, which only serve to produce a stronger magnetic development in the core, and consequently a stronger wave when it suddenly returns from the magnetic to the normal state.

In the machine, however, which I have introduced to the notice of the Association, the magnetic changes of the iron core are always maintained at their maximum degree, and the amount of secondary current employed is therefore not governed by any modifications in the magnetic intensity of the core, produced either by the uncertain and objectionable modes of increasing battery power, or inserting and withdrawing the iron core, but by varying the length of secondary coil embraced in the circuit by accurately measured increments, each of which adds a known quantity to the general effect.

The action of these intermittent currents is precisely analogous to that of the leyden jar of the frictional apparatus, differing only in degree.

Each small impulse arises from the transmission of a minute though definite quantity of electricity, in a given direction, through a portion of the system included between two rheophores, and may be confined to a very small spot, or may embrace the whole length of the body from head to foot.

As in the leyden jar the quantity can be increased by extending its surface, so in the machine before the Association the strength is increased by bringing into action a greater length of wire; the resulting pathological symptoms are therefore precisely similar in character in each case, and are purely electrical. It is thus clear that since the current developed by the reaction of magnetism increases in proportion to the length of secondary coil, the battery and primary coil remaining the same, the extent to which the power may be accumulated is indefinitely great; but for therapeutic purposes, I find a range of from 20 to 32 of my standard units of force adequate for all therapeutic purposes.

VOLTAIC ELECTRICITY.

We now come to the consideration of another form of administering electricity, namely, the Voltaic, Galvanic, or Continuous Current.

About half a century since, attempts were made, with various degrees of success, to substitute Galvanic or Voltaic Electricity for that obtained from the glass frictional machine. The galvanic troughs invented by Cruikshank, and improved by Dr. Wollaston, were called into requisition; but although they presented less difficulty in their management than the frictional machines, which required skilful manipulation, and the adjunct of fine weather for their success, they were scarcely less objectionable, on account of the inconvenience of using acid to excite them.

I believe I was the first to make a portable Voltaic Battery. It was based on the principle of Volta’s Pile, and consisted of circular discs of copper and zinc, soldered together in pairs, perforated by a hole in the centre, and strung upon a horsehair line, with discs of cloth to separate them from each other. This little battery, being armed with flexible wires and suitable rheophores, was, after being moistened with vinegar, either rolled up in oil-silk and carried in the waistcoat pocket, or inserted in the hollow handle of a walking- stick, or in the walking-stick itself; and I know of none of the miniature contrivances, in the form of chain bands, &c., which surpass this in efficacy, as far as it goes.

It was, however, like all analogous contrivances, too transient in its action to be of very general use, and Voltaic Electricity received a sort of deathblow when Faraday made his great discovery of Magneto Electricity.

Of late years, however, the use of the Voltaic or Continuous Current appears to have gained favour among the Continental therapeutists, and the translation of the results of their labours into English has excited a considerable amount of interest amongst the medical profession in London and elsewhere.

Several elaborate and ingenious forms of apparatus have been contrived for applying the Continuous Current, but they all possess the rather objectionable qualities of costliness and want of portability.

This has induced me to turn my attention to the subject, and I believe I have succeeded in producing a Continuous Battery which combines simplicity with efficiency and readiness of action, power with economy of space, and above all, economy of price.

The little battery which I have the honour to exhibit to the Society contains fifty elements, developing a power sufficient for all therapeutic purposes in a space of 12 x 8 x 11 inches. It is always ready for use, requiring merely that a trough of dilute acid contained in the bottom of the box shall be raised so as to immerse the plates for a few moments, and then lowered again.

The quantity of acid retained by each of the fifty elements is sufficient to keep the battery in action for some hours; any decrease of power is instantly restored by repeating the immersion for a moment.

The zinc plates consist of strips of stout zinc half an inch wide and four inches long, fastened in rows to a plate forming the cover of the box, and projecting down into the interior.

Each plate of zinc is first amalgamated, and then surrounded by a piece of cloth, round which is wound spirally a copper wire so as to leave interstices between the coils.

One end of each coil is left long enough to solder fast to the next plate of zinc, so as to keep up the continuity of the series from one end to the other.

An arc of ten metallic buttons is placed on the upper plate, having stems which project into the interior. Over these buttons a metallic spring hand passes, and wires from the ends of the metal stems within are connected respectively with five, ten, fifteen, up to fifty of the elements in a series below; thus giving the facility of modifying the power at pleasure.

The whole of the interior in working order lifts out of the mahogany case which contains it, and the portability is such that even with a little care it may be carried about without spilling the acid contained in the trough below.

For my own part, I am quite satisfied with it as a practically useful instrument, and my experience in these matters extends over nearly half a century. I make a more powerful form of this battery by substituting small platinised silver plates for the copper coils, and giving each element a small glass cell in which to retain the acid, the latter being lifted as before simultaneously for the purpose of exciting it.

Medical science is and will be greatly indebted to the earnest labours of those who are now prosecuting Electro-therapeutic investigations in relation to the Continuous Current, and I would venture with deference to throw out a few suggestions which may not be unworthy of consideration.

Two great principles have to be borne in mind in relation to the transmission of electricity, namely, electro-motive force, and resistance.

We hear much of the great desideratum – a constant continuous battery; that is, I presume, a battery always ready to yield a current of uniform strength.

Time will not permit me to show that this is about as feasible as perpetual motion; but, limiting the period of its constancy within practical bounds, uniformity of effect is impossible when the circuit upon which it operates varies in its conducting character. The amount of current flowing between two terminals will vary with every change of position on the surface of the human body.

Thus no two effects can be correctly compared, since the currents producing them are constantly varying.

If a current from half a dozen couples be flowing with a certain intensity through a certain portion of the body, the shifting of the rheophores a few inches will so vary the resistance of that part of the circuit as to require the employment of a greater or less number of elements to enable a current of equal force to be transmitted. My new battery, however, meets this difficulty at once.

Again, before correct therapeutical deductions can be drawn, the electrical functions and character of the various tissues and nerves, both under normal and abnormal conditions, have to be more correctly ascertained.

The difference in the conducting character of muscles and nerves is extraordinary; and even muscular fibre varies in the resistance which it affords to the electrical currents, accordingly as they are transmitted transversely or longitudinally through its mass, or through its nervous or tendinous attachments.

This can be easily and practically demonstrated in the following way.

Let two individuals be included in the same Faradaic circuit, one holding permanently a pair of metal handles, whilst the circuit is completed by including within it different portions of the body of a second subject. The one holding the shock handles will be sensibly aware of the difference of effect produced upon him when various portions of the muscles or nerves of the second subject are included in the circuit; and it is a curious fact that, whenever the nervous or muscular excitement is greatest in the subject submitted to treatment, the sensation is correspondingly great in the one acting as the rheoscope.

Time forbids me to extend the length of this paper. I must therefore close by remarking, that it is scarcely possible in abnormal conditions to apply electricity to corresponding portions of the body on opposite sides, without discovering a marked difference between the susceptibility of the two limbs to electrical influence, either in regard to sensory or motor power.

Much will have, for a long period, to be gained by empirical observation, and a careful registration of observed facts, since the most unexpected results are daily obtained under circumstances which no prognosis would have indicated.

The instruments which I have brought before the notice of the Association will, from the uniformity of their action and construction, not only assist in the comparison of results amongst different experimentalists, but, from their peculiar adaptability to therapeutic purposes, facilitate the application of electricity as a curative agent.