Very extensive destruction of cancerous tissue is accomplished by the introduction of metallic ions from large zinc needles amalga mated with mercury and connected with the positive pole while the patient lies upon the large indifferent negative electrode.
Anaphoresis or the introduction of acid radicals which the current carries toward the anode, is illustrated by the introduction of salicylic ions from a cathode wet with a solu tion of sodium salicylate, in rheumatism and neuralgia.
The old theory about the use of electricity in paralysis was that the involuntary contrac tions produced by the abrupt makes and breaks of the galvanic current and especially as we shall see later by the faradic current, tended to maintain the nutrition of the paralysed muscles until regeneration of the nerve took place. Certainly the patient and friends could see that something was happening during the application. It is doubtful whether the con tractions accomplish this and in some cases of paralysis it is thought that the contracture or permanent shortening of some muscles, difficult or impossible to overcome by manipulation, may be aggravated by electrical treatment of a nature to produce marked muscular movements. The passage of the galvanic current itself has a tendency to maintain the nutrition of the muscles and to aid in the regeneration of the nerves. And by means of the apparatus in Fig. 3, a galvanic current sufficiently strong to produce the maximum benefit may be applied without the disadvantage of electrolysis and possible skin irritation at the electrodes and especially without any noticeable muscular con tractions.
This current is a slow sinusoidal current or a rythmically varied galvanic current increasing from zero to a certain maximum, 18 or 20 mil liamperes in one direction; then gradually de creasing to zero; then changing polarity and gradually increasing to 18 or 20 milliamperes; then gradually decreasing to zero where the polarity again changes. About 25 such cycles occur each minute under the influence of variable rheostat and pole changer actuated by an electric motor. This type of current is use ful in paralysis from poliomyelitis and apoplexy and also as a general tonic in many debilitated conditions and also in cases with vertigo from affections of the cerebral or cerebellar circula tion.
Another effect of the galvanic current is to stimulate the secretion of glands. Another is to promote the return of sensation in paralysis of a sensory nerve. By its sclerolytic effect it aids in the treatment of pleuritic adhesions and of anchylosis or joints stiffened by some previ ous inflammatory condition. Calvanic elec tricity has a sedative or calming effect valuable in many general disorders and this effect is often best produced by hydroelectric baths. Its analgesic effect makes it valuable in the treatment of neuritis and neuralgia.
Faradic electricity is made up of alternating currents induced in a coil with many turns of insulated wire surrounding a coil with few turns of wire through which passes a current rapidly made and broken by a vibrating inter rupter. The faradic current is of very small electrical quantity as measured by its heating effect. A couple of dry cells may supply the current for a portable faradic coil but for an office equipment the electric light circuit suit ably controlled is best because it does not re quire renewal and affords also power for the galvanic, galvanofaradic and sinusoidal cur rents. It produces marked muscular contrac tion of a tetanic type continuous during the entire time the current is applied, not merely at the beginning and end as with a galvanic current.
Two electrodes are necessary for applying the faradic current; one of which may be at an indifferent place. And in contrast with the galvanic current there is usually no difference in the effect of the two electrodes, practically no polarity. Testing the faradic excitability of a muscle or nerve is an important part of electrodiagnosis, but, as explained above, the treatment of paralysis through involuntary muscular movements induced by faradic stimu lation is not always best. Faradic currents from a secondary coil with a comparatively small number of turns and a slowly vibrating interrupter, are more effective in producing muscular contractions, and a great many turns of wire in the coil and very rapid interruptions are best for producing a sedative effect upon neuralgic nerves.