Condensers having a great many square inches of condensing surface interleaved like a book may be charged from the two poles of a galvanic battery. They receive a very large charge at a low voltage; and when they are discharged through the human body they pro duce marked muscular contraction. Since the capacity of the condenser and the voltage to which it is charged can be regulated. these low tension condenser discharges form a very exact means of electrodiagnosis. They may be used for treatment chiefly of paralysis, and for some of the same purposes as the static induced current.
The modern static machine, also called an influence machine, has its initial charge pro duced by friction upon a revolving glass plate. This is communicated to other glass or mica or fibre plates arranged in such a manner that as they revolve the mutual attractions of positive and negative static charges separated by insulat ing disks, result in the accumulat'on of very strong charges at the two poles of the machine.
Static insulation or the static bath is ap plied by connecting one pole of the machine with an insulated platform upon which the patient is seated. A static breeze is a silent, almost invisible discharge from a metal crown with sharp points connected with one pole of the machine, suspended within 6 or 12 inches of the patient. The effect is increased if at the same time the patient is insulated and receiving a static bath from the other pole of the ma chine. Static sparks are applied by bringing near any part of the patient, either clothed or not, a metal ball having an insulating handle and connected by a flexible conductor with one pole of the machine. Here, again, the effect is intensified if the patient is insulated and receiv ing a static bath from the other pole.
The static induced spark is described in another paragraph.
The Morton wave current is a bipolar appli cation from the two poles of the machine by two wet electrodes which make a very perfect contact with the patient to avoid any spark effect. The patient had better be upon an in sulated platform. The discharging rod.; of the machine are only a fraction of an inch apart The greater their distance, the more powerful and even intolerable the effect becomes.
Every possible connection with and without Leyden jars has been used in treatment. They all have distinctive names but the arrangements described are the most important Effects of Static Electricity.— A single
spark produces a muscular contraction and a sensation of local shock which is not very dis agreeable. It is applied by striking at but not touching the patient with the insulated metal ball and quickly withdrawing it; somewhat the motion of cracking a whip. A dozen separate loud sparks applied along the spine are easily received by the most sensitive patient. But it is a very different matter ? ' en the ball elec trode is held near the skin and a steady stream of sparks is applied at one place. That is intolerable. Static sparks are used as a general tonic in debilitated states and as a counter irritant for removing any old inflammatory products. They are not suitable for electro diagnosis or for the treatment of paralysis. The static bath is a general tonic in debilitated states including convalescence from illness or operation and exhaustion from the care and anxiety attendant upon the illness of some dear one. It is excellent in neurasthenia and in insomnia. It is frequently combined with the static head breeze, and, except for insomnia, with the application of sparks along the spine. The static induced current has effects similar to those of the wave current but less useful.
Morton's wave current produces a succession of muscular contractions which should be slight. It is of value in relieving hyperemia and swelling and pain, and is used in the treatment of a great many chronic conditions in which these are prominent symptoms.
High Frequency Currents.— When a con denser is discharged by touching its two metal surfaces, the result is not an immediate change to an uncharged condition in each metal sur face. Taking the surface that was positively charged we find that its charge drops not only to zero but to a certain distance on the nega tive side then back to zero and a certain lesser distance in a positive direction and so through thousands of oscillations in a small fraction of a second it comes to rest at zero. The oscilla tions are analogous to the vibrations of a piano wire after being pulled out of a straight line and released. The static induced current is the simplest example of a high frequency current but the discovery of the D'Arsonval current and of the resonator current has lately added a method of wonderful value.