The auditory reactions to the appli cation of electricity form a very delicate and important means of the of lesions in the labyrinth of the ear. For example, one of the normal re actions is obtained when an electrode is placed in front of the tragus of each ear and a galvanic current is applied. The patient feels dizzy and the outside world seems to be moving toward the cathode and the head is inclined toward the anode. He may see sparks before the eyes and hear a noise in the ears, and if the current is quite strong there is nystagmus or oscillation of the eye balls.
A sensation of taste accompanies any application inside the mouth and often applications to other parts of the face.
The heating effect of electricity is well known but suitable galvanic cur rents are so weak that the sensation of warmth or even the reddening of the skin in contact with the electrode is usually due to electrolysis and not to the frictional resistance to the passage of the current. Very heavy galvanic currents of over 100 milliamperes, ap plied inside the uterus in the Apostoli treatment for fibroid tumors, did pro duce a great deal of heat but treatment by radiotherapy (X-ray and radium) is now more usual.
— Instruments which are connected with both poles of the battery so that no current passes through the patient, are arranged so that a certain part becomes red hot owing to the passage of a Co.) current through a thin metal strip in the same way that the filament in an electric light bulb is 'heated by the passage of the current. Only the portion which is to be applied to the diseased surface becomes appreciably hot because the conducting wires are larger and capable of transmitting the current with less resistance. Familiar examples of galvano-cauterization are in the treatment of growths in the nose and larynx.
Electrolysis is an effect of the passage of a constant current through an electrolyte such as the human body. A chemical compound such as water is separated into its elements such as hydrogen and oxygen, and in the case of the human body an accumulation of sodium hy drate and a liberation of oxygen take place at the negative electrode and an accumulation of hydrochloric acid and a liberation of oxygen at the point of contact with the positive elec trode. If the negative electrode is a fine needle thrust into a hair follicle, a current of about four milliamperes causes a liquefaction of the tissues and loosening of the hair, the root of which may be permanently killed. A needle
connected with the positive pole of the battery would stick fast and could not be withdrawn until a negative current had been turned on for a short time to loosen it by liquefying the tissue around it. The (modal needle has a coagulating effect. Electrolysis is employed also for the destruction of warts, birth-marks and keloids, in the treatment of strictures of the urethra and oesophagus and such lesions as anthrax.
For most of these cases the Indifferent" electrode is a sponge electrode held in the patient's hand; but for a more extensive destruction of tissue, needles connected with each pole of the generator are used and the needles are near enough together for all the intervening tissue to be destroyed. Rhy nophyma, a bulbous swelling of the nose, is re moved in this way.
Iontophoresis, including Cataphoresis and A galvanic current tends to separate the electrode itself or the solution with which it is moistened into ions and to carry these into the tissues, iontophoresis. Metals and alkalis are carried toward the negative electrode or cathode and the introduc tion of these ions by an electric current is called cataphoresis. For example the positive electrode may be moistened with a solution of a cocaine salt and the cocaine will penetrate the tissues ; they leave the anode and pass toward the cathode but their anesthetic effect is upon the tissues into which they first penetrate.
Some of those who have experimented most with iontophoresis assert that it is a more re liable way of administering many drugs, than giving them either by the stomach or hypo dermically. Two rabbits were experimented upon by Leduc, as in Fig. 2. Rabbit A died with symptoms of strychnine and rabbit B of cyanide poisoning. Two other rabbits were subjected to the same experiment except that the direction of the current was reversed so that the strychnine ions did not tend to enter rabbit A, nor the cyanions the rabbit B, and neither was poisoned.
Another example of cataphoresis is electric ionization of the root canals of devitalized teeth. The positive active electrode may be a zinc needle moistened with a solution of a zinc salt. The method is employed to remove in fection from the root canal and the area of the jaw around the apex of the root.