High Frequency Resonator Discharges.— The Oudin resonator shown in Figure 5 is an apparatus for this purpose. The outer coat of one of the two Leyden jars is connected with the end of a wire spiral and the outer coat of the other with some part of the spiral between its two ends. With each discharge of the Ley den jars, a current passes through the turns of the spiral between the two connections and this induces a current passing toward the free end of the spiral and increasing in voltage until from its terminal a long spark or a violet colored effluve may be drawn; or a glass vacuum electrode may be used to apnly this high tension high frequency current. The ap plication is a unipolar one. When the vacuum electrode is held near the surface of the body a shower of sparks passes to the sltin and this may be more or less disagreeable. This spark effect is largely avoided by keeping the electrcxle in contact with the surface. But even then tiny sparks may be seen passing from parts of the bulb not in "close contact with the skin. These are not disagreeable. A sensation of warmth is produced and the entire glass vacuum tube becomes heated in proportion to the strength of the high frequency current. The glass stem where the current enters from the insulated handle and the surface in contact with the patient are hotter than other parts of the electrode. The bulb is filled with a violet and ultraviolet light. The latter is invisible but its presence is easily demonstrated by fluoresence induced in Willemite. It doubtless is partly concerned in the effect produced upon the tissues.
High frequency currents have little or no tendency to produce muscular contraction and are not used for electrodiagnosis. The spark effect is useful as a general tonic, to stimulate sensory nerves, to cause constriction of blood vessels locally and vasodilitation generally. Sparks applied from a metal point held close to the surface have a counterirritant or a destructive effect depending upon the strength of the current and the length of time sparks are applied to one spot without intermission.
D'Arsonval currents, locally, raise the tempera ture and increase the circulation, increase the activity of glands and are a sedative. Autocon densation increases the production of heat in the body, increases the urinary solids and acts as a sedative. And especially it reduces the blood pressure when that is unnaturally high. The vacuum electrode actuated by the Oudin resonator has the effect of heating the tissues and promoting cellular activity of every kind as well as increasing local circulation. It is a counterirritant when the current is strong or is so regulated as to nroduce considerable spark effect even with the electrode in contact with the surface. In this case its general effect is stimulating; hut with the current adjusted to produce very little spark effect and a great deal of warmth from the vacuum electrode in contact with the skin it has a sedative effect, and tends to reduce unnatural high blood pressure.
Some of the conditions treated by high frequency applications are growths varying from warts to skin cancers; various skin dis eases including acne; high blood pressure and arteriosclerosis or hardening of the arteries; rheumatism; gout; neuritis and neuralgia; angina pectoris; hemorrhoids.
Bibhography.-Consult Gould and Pyle, of Medicine) (Philadelphia 1912); Guilleminot, 'Electricity in Medicine) (New York 1906) • Jones, 'Medical Electricity> (6th ed., Philadelphia 1913) ; Martin, 'Practical Electro-therapeutics) (Saint Louis 1912); Neiswanger, 'Electro-therapeutical Practice) (18th ed., Chicago 1912) ; Rockwell, 'Electricity in Medicine) (New York 1904) ; Tousey, S., 'Medical Electricity and Roentgen (Philadelphia 1910, 1915).