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.|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.
LECTURE II.
METHODS OF APPLYING ELECTRICITY.
Gentlemen,
Résumé of First Lecture.
In our first Lecture we studied the different kinds of electricity employed in medicine, and the construction and management of batteries. I reminded you that we made use of three kinds of electricity; firstly, of friction or static electricity, Franklinism; secondly, of the electricity of chemical action, Voltaism, or Galvanism; and, thirdly, of induced electricity, Faradism:—that there had been certain difficulties in the employment of Franklinism, but that these difficulties no longer existed; that Voltaic electricity was electricity in motion, or current electricity, but that while its current (unless artificially interrupted) was always continuous—flowing, that is, in an unbroken stream—and from the positive to the negative pole, until the battery was exhausted—it by no means followed that it was constant, that is, that it did not vary appreciably in power during application; that only batteries supplying a fairly constant current were fitted for medical use, and that all others should be rejected. We then considered different batteries, both fixed and portable; that while large fixed low tension batteries were unquestionably superior in their therapeutic effects, patients unfortunately were not always movable, and that a portable battery became, therefore, a sine quâ non; that portable batteries might be conveniently divided into two classes, one in which electricity was generated by the elements being immersed in an exciting fluid only during actual use, and being taken out of the fluid immediately after use; and the second that in which no removal of the elements was necessary; that the Voltaic current was graduated into doses by some arrangement determining the number of cells to be employed in each case, but that this method, while practically useful and sufficient, failed to convey an exact idea of a measured and unvarying quantity of electricity; and that it had been contended that by the use of a galvanometer, doses of electricity might be as accurately administered as so many grains or minims of ordinary medicines, but that, perfect as the theory might be, I had personally failed to obtain help in practice from a galvanometer; that next in importance to a method of dosage, was it to be able to instantly change the direction of the current, or to at once turn it “off” or “on,” in addition, of course, to the fundamental requisite of a continuous supply of electricity of sufficient quality and quantity.
We next considered the induced or Faradaic current, so-called, which I reminded you is not a current at all, but a rapid discharge or succession of those momentary shocks, each perfectly distinct in itself, and separated by an appreciable interval of time from its fellows, which Faraday discovered to be generated or induced by a Voltaic current flowing along a wire in other wires parallel to, but separated from, the first wire; that by winding the two wires upon two movable reels and introducing one within the other, not only might these secondary currents be multiplied indefinitely in proportion to the number of spirals of wire, but by introducing or withdrawing the one from within the other an exact method of graduation was afforded us. I pointed out to you that there was no therapeutic distinction between the so-called primary and secondary currents, and I recommended you therefore to use only the currents of the secondary coil. I then showed you the construction of Faradaic instruments, and of instruments combining both Voltaic and Faradaic currents, and our survey was completed by a consideration of the different varieties of conducting wires or cords, and my recommendation of thin gutta-percha covered copper wire as generally superior to any other form. We have to-day to study methods of applying electricity, and to learn how to use the instruments, with the construction and properties, of which I trust you are now familiar; and, Gentlemen, it is well worth your while to have obtained this knowledge, for its possession will not only enable you to readily rectify any faults in the working of your batteries, but the necessity of sending them to the instrument-maker may be often avoided.