Part 2

The Voltaic current is a _continuous_ current. Unless artificially interrupted, the electricity flows in an unbroken stream until the battery is exhausted. The current will gradually lessen in power until it ceases, but there will be no break in it, and no change in its direction, which is uniformly from the positive to the negative pole. [SN: Points of distinction between the Voltaic and Faradaic Currents.] It is important to recollect these points, for they constitute the chief physical distinction between the Voltaic and the Faradaic--or, as it is sometimes called, the Induced current. This latter is not, strictly speaking, a “_current_,” but a rapid discharge or succession of momentary shocks, each perfectly distinct in itself, and separated by an appreciable interval of time from its fellows.

[SN: Voltaic Cells.]

In electrization, a source of electricity is of course necessary, and this is furnished by a cell or cells, with contained elements and chemicals; and, until a few years ago, it was impossible to get a _portable_ cell that remained always in order and ready for use.[7]

[SN: Requisites of a Portable Battery.]

The requisites of a portable battery are that it should be really portable, always ready for use, and little liable to get out of order. Such batteries may be divided into two classes: firstly, those in which the elements are either lowered into the exciting fluid or the fluid is lifted to them, as in the instruments of Stöhrer, Weiss, and almost all other makers; and, secondly, those in which the elements remain immovable in their cells, and of these the Leclanché, the Gaiffe-Clamond, and the chloride of silver, are to be generally preferred to any of the first-named construction, for they admit of the cells being so nearly sealed up that no fluid can be spilt by any movement except turning the battery quite upside down; while the somewhat common accident with batteries of the first-named construction--viz., destruction of the plates by leaving them in the acid, with its anything but agreeable result of a considerable expense to replace them, is obviously impossible. The only disadvantage they possess is that when exhausted it is necessary to send them to the maker to be recharged, _while the owner can keep the first-named variety in order himself_.

Efficient cells are, however, but a first step to the perfection of electrical apparatus, and the mechanism by which the current is brought into use and graduated, and the general accessories of the instrument, are of at least equal importance. The instruments which I am about to describe, have been designed by myself, and may be obtained from Mr. Hawksley, Surgical Instrument Maker, Oxford Street. It is claimed for them that they place at the service of the busy practitioner a battery that with ordinary care (and no instrument will remain in order without this) may be kept upon his consulting-room table, always as available to his service as his stethoscope or ophthalmoscope.

Three kinds of batteries are constructed:--A Voltaic battery, with any required number of cells, from 15 to 100; a Faradaic battery; and a Combined battery, uniting both Voltaic and Faradaic currents.

[SN: The Voltaic Battery.]

_The Voltaic Battery_ (see Fig. 6, p. 20) has its cells arranged in the interior of a mahogany case, and in use they are hidden from view and from danger, but I now partially expose them by removal of the tray for holding the sponges and accessories. Their connecting wires are brought across the under surface of the element board, which is made to move upon hinges that, when necessary, the cells may be examined, but at other times this element board is held in position by a bolt, and it should never be needlessly disturbed. These wires conduct the current through the graduating dial, and the position of the needle of this dial determines from how many of the cells the electricity shall be allowed to reach the binding screws, and from them, by way of the conductors, sponge-holders, or electrodes, the body of the patient,[8] or whether it shall be entirely shut off, as is the case when the battery is not in use, and when the needle stands at “0” (Fig. 7). When the needle points to any stud numbered on the dial, the number of cells marked on that stud are brought into action, and the needle is made just wide enough to touch one of the studs before it breaks contact with the preceding one, and thus the current may be increased or decreased in power without shock, and while the electrodes are held applied to the patient; but if it were not so made a series of painful shocks would be communicated whenever the current was increased or decreased. Should the needle, from forgetfulness, be left when out of use in any other position than at “0,” a guard upon the lid of the instrument prevents its being shut, and the operator has his attention called to his inadvertence. A Voltaic alternative, or change of direction of the current, is sometimes required in treatment, and the commutator of the poles enables this to be accomplished without alteration in the position of the conductors. By pushing forwards or backwards the handle which moves a lever working below the element board the current is instantly reversed, and the alternation of the letters “P” and “N” seen through holes cut in the element board indicates at once not only that there has been a change of poles, but which pole is at the moment negative or positive; whereas in all previous instruments, when the poles have been changed, there has either been no letter marking them, or this letter has really been wrong, and one has had to remember this; and under such circumstances, and examining patients in rapid succession, momentary confusion of the poles was very liable to occur, even to a practised operator. A key enables the current to be shut off or on without removal of the conductors. Dirt is a non-conductor of electricity, and the studs of the dial must be kept clean with emery paper or plate-powder, as also the under surface of the needle, key, and binding screws, which unscrew to admit of removal. In the daily use of a battery the chief work is usually thrown upon the first half (say in a battery of forty cells, upon the first twenty-five), and various arrangements have been added to batteries by ingenious instrument-makers to enable the operator to vary his selection of the cells to be brought into use, and thus to relieve the first half of his battery, or, in other words, to equalize its work. But this unequal work question is more a theoretical than a practical evil; for if the initial cells grow weaker a greater number can be placed in use. I have carefully studied all the proposed modifications, and have found in all of them the remedy worse than the disease, unless the graduating dial be doubled (an original suggestion of my own), so that the initial cells of one week may be made the terminal cells of the next.

When desired batteries can be constructed with this double dial (Fig. 8), but it adds to the complexity of the instrument, and I do not myself use it.

In Fig. 9 a similar battery is shown to that just described; but the elements consist of carbon and zinc, and are lifted into and out of a bichromate solution. As it can be recharged by the owner without the necessity of sending it to the maker, it is especially suited for country and colonial practitioners.

[SN: Essentials of a Medical Voltaic Battery.]

To recapitulate. The essentials of a medical Voltaic battery are--

_a._ A constant supply of electricity of sufficient quantity and quality.

_b._ A means by which this electricity may be administered in measured doses.

_c._ A means by which the direction of its current may be changed.

_d._ A means by which it may be instantly discontinued.

FARADISM.

[SN: The Faradaic Current.]

The Faradaic, induced, interrupted, or electro-magnetic current, is the third form of electricity employed in medicine. Faraday, as you will recollect, discovered, that if two metallic wires were so fixed as to be parallel and close to each other, but not to touch; and that if then a current of Voltaic electricity were sent along the first wire, another current appeared in the second. This _secondary_ or _induced_ current, as it is called in contradistinction to the current, the _primary_ or _inducing_ current sent along the first wire is only momentary, but it appears again for a moment when the first current ceases, but in a reverse direction. It is most convenient to wind these two wires round two reels, so as to form separate coils, and to place the primary within the secondary coil. Each single turn of the primary then acts not only on the parallel turn of the secondary wire, but on all the turns near it, and the power of such an apparatus is much greater than that which would be obtained by the same lengths of wire running side by side in a straight line. Our two coils being thus arranged, we pass through our primary wire a succession of electrical currents, and in practice this is accomplished by connecting its extremities with a battery supplying a continuous current, which by an ingenious mechanism we frequently break or interrupt.

[SN: The Faradaic Battery.]

_The Faradaic Battery._--In Fig. 10 (see p. 29), a Faradaic battery, worked by two Leclanché cells, is shown; but I find it better to employ either one or two ordinary bichromate cells instead of the Leclanché, as the former can be kept in order by the operator himself without much trouble. The primary coil is fixed upon a pedestal, the secondary is movable, and can be lifted over or thrust away from the primary. The degree of action in the secondary coil being proportionate to the extent to which it is brought under the influence of the primary, this arrangement admits of the most perfect graduation of the current; and it has been for some time in use in all well-constructed instruments. The innovation I have made consists in limiting the primary coil to its legitimate purpose of induction, and rendering the secondary alone available for application to a patient. I have been long satisfied that therapeutically the distinction between the primary and secondary coil entirely consists in the greater tension of the current of the secondary coil enabling it to penetrate easily several thicknesses of muscle, but there is no therapeutic indication that cannot be fulfilled by this secondary coil; and at its lowest power I have frequently applied it to the conjunctiva. The rapidity of vibration of the interrupting hammer is varied by increasing or decreasing the distance between the point of the needle and the electro-magnet by the protrusion or retraction of the screw, of which the needle forms the end--that is, by increasing or decreasing the space through which the hammer passes in its vibration, and also by altering the pressure of its spring, but there is seldom therapeutic need for change of vibration; and unless this exists it is better _not to alter the adjustment so long as the instrument acts well_.[9] After considerable use the point of the needle, and the exact spot of the platinum disk of the hammer against which this needle impinges, become oxidized, causing weakening or stoppage of the current. This platinum disk has been constructed to rotate, and a hole has been drilled in its circumference (Fig. 11). By inserting a little lever furnished with the instrument into this hole, the slightest twist given to the disk is sufficient to bring a new surface of platinum into contact with the needle point. This will usually be all that is required, but, if not, the needle can be unscrewed, and its point cleaned with emery paper. When in course of time the disk becomes dotted over with spots of oxidation, the screw fixing the hammer in position must be unscrewed, the hammer lifted out, and its surface similarly cleaned.

Induction currents are also produced in coils of wire by the action upon them under certain conditions of a permanent magnet--as in the ordinary rotary magneto-electric machine--but these machines may be discarded from our consideration, for they are uncertain in action, painful in application, and do not admit of exact graduation.

An apparatus in which both currents are combined is extremely convenient if it is so constructed that either the Voltaic or Faradaic current can be brought to the same terminals, thus avoiding the trouble of changing the conductors--a point of the greatest possible convenience when examining patients for diagnostic purposes by both forms of electricity, either in succession or alternately.

[SN: The Hospital Combined Battery.]

In the _Hospital Combined Battery_ (see Fig. 12), constructed from my designs, the two currents are thus united, and its details are precisely similar to those of the separate batteries, with the exception of the Dial being furnished with an additional stud lettered _Coil_. When the needle points to this stud the current from the Faradaic coil is brought into action; when it points to the numbered studs, the cells numbered thereon as in my Voltaic instrument, and when it points to “0,” both currents are shut off.

Other instruments, such as those of Stöhrer and Weiss, are excellent, and were unsurpassed until the invention and improvement of the Leclanché and other cells. But I might talk upon instruments for hours without exhausting the list; and I have felt obliged to limit myself to a description of those I believe best fitted to our requirements; but it, of course, must be understood that my further _observations will apply equally to currents of electricity furnished by any properly constructed and reliable apparatus_.

[SN: Accessories of the Battery.]

We have now brought the electricity to the terminals of our battery, and we must next consider the best means of conveying it to the sponges, conductors, or, as they are generally termed, rheophores or current carriers, by which it is finally applied to our patient. [SN: Conducting Cords.] Our first necessary accessory is a conducting cord or wire, and it is of the first importance that this should really be what it is called--“_a conductor_”--for any fault or break of connection in it will, of course, nullify the best and most perfect battery. It must also be sufficiently pliable, and be insulated by being coated with some non-conducting material that the electricity may not escape from it to any conducting substance with which it may accidentally come into contact. The conducting cords sold by instrument-makers are sometimes not insulated at all, and then they are quite useless, but they are more commonly composed of several strands of metallic wire of about the diameter of sewing thread, the whole enclosed in some silken or woollen material, and nothing can be better than these latter when quite new. Their disadvantages are that they become frayed after a little use, and are liable to be constantly out of order, causing interruptions in the current, while they will only fit one kind of machine. I have had endless trouble with them; and for some years I have used nothing but thin copper wire, coated with gutta percha in the same way as that known as “telegraph wire.” This is perfectly insulated, sufficiently pliable for all practical purposes; it is cheap, and can be made to fit any sort of connection. Its one disadvantage is, that it is liable to break at the point where it is received into the terminals of the battery, or the screw socket of the rheophore. Should this happen, all that is necessary is to scrape off the gutta percha coating with a pocket knife for an inch from the broken end, by which we get practically a new conducting cord.

We have now considered fully the birth and parentage of medical electricity, and we have conducted it to within almost a hair’s breadth of our patient. The various methods of applying it will be considered in our next Lecture, which I trust, Gentlemen, to render more interesting; but the dry details we have been discussing are, I assure you, essential as a secure foundation for a practically useful survey of electro-therapeutics.

FOOTNOTES:

[1] See “Vital Motion as a Mode of Physical Motion.” By C. B. Radcliffe, M.D. Macmillan.

[2] See Mr. Netten Radcliffe upon the differential reaction of voltaic and induced currents of electricity. Note to page 331, vol. i., of Bazire’s translation of Trousseau’s “Clinical Medicine.” Hardwicke.

[3] This observation, made in 1873, requires some qualification now (1886). At several of the great medical schools, though not at all, electrical treatment has been transferred from the hospital porter to some member of the hospital staff; and at more than one a systematic course of lectures upon electro-therapeutics has been delivered.

[4] I speak feelingly upon this matter, for from an early period of my electrical experience I have suffered much from batteries--from instruments “striking work” at the most inconvenient moment--from spilling of corrosive acid upon fingers and clothing, to the detriment of both, and of temper too, I fear.

[5] So long ago as 1870, I was in the habit (at the suggestion of Dr. Radcliffe) of employing at an Institution for Resident Patients, a method of “charging” a patient which I believe to be unique.

[SN: _Unique method of charging a patient._]

During dry summer weather the patient reclined upon a couch in the gardens insulated by glass supports, and a sort of lightning conductor was improvised by attaching a 30-feet salmon-rod to the foot of the couch, a piece of ordinary “telegraph wire” being carried up the rod, its insulation being removed from about a foot which projected above the top of the rod.

Upon a fairly warm and dry day the patient became “charged” and sparks could be drawn from him as from a patient in ordinary connection with a Franklinic machine in rotation.

Upon more than one occasion in those ancient Static days, an attempt was made to insulate a patient for a whole night, and to maintain the charge by a relay of “rotating nurses;” but the _human machines failed_, and suitable gas engines were not then available; hence the procedure related above was, if conducted for three or four hours on a dry summer afternoon, a by no means bad substitute for a close room and a rotating Static machine. In New York, in winter, when the rooms are covered with thick carpets, and when the atmosphere is dry, it has been known that on shaking hands with a visitor, not only has the “shock,” which under similar circumstances occasionally occurs in England, been felt, but that a spark has passed; and children have been known to slide over the carpet towards each other and exchange sparks by way of sport. _The influence of atmospheric and other ordinary electrical conditions has been far too little studied by electro-therapeutists._

[6] The Carré Machine can be obtained from Mr. Groves, 89 Bolsover Street; the Fly Wheel from Messrs. Hovenden and Co., Great Marlborough Street; and the Gas Engine from Messrs. Andrew and Co., Engineers, Stockport.

[7] Currents of electricity from large fixed batteries are most marked in their curative effects; but patients are not always movable!