High frequency currents : their production, physical properties, physiological effects, and therapeutical uses

Preface

In submitting this book to the English-speaking members of the medical profession, the author hopes that it may in some way help to bring before the notice of medical men the undoubted therapeutical value of high frequency currents in certain pathological conditions.

On the Continent, and in the United States of America, the efficacy of the currents is well known, and much good work has been accomplished by their means ; but in England, it would appear, they have not met with the recognition they deserve,' possibly because they unfortunately have, in many instances, fallen into the hands of irresponsible, unqualified persons.

It cannot be too strongly insisted upon that the prescribing and administration of high frequency currents should be placed entirely in the hands of properly qualified medical practitioners, and not entrusted to others who may be devoid of any physiological or pathological knowledge. It stands to reason that a powerful agent, having far-reaching physiological effects, requires as much skill and discretion in its use as the exhibition of any drug in the Pharmacopoeia.

It remains for the author to express a sense of deep gratitude to Mr. Clarence A. Wright, who has most kindly allowed him free access to many of his manuscripts ; to Mr. Geoffrey Pearce, who has been of great assistance in matters relating to instrumentation ; and to various instrument makers who have kindly lent " blocks "

for some of the illustrations.

H. E. C.

ivermore,

Richmond Road, Twickenham.

September, 1906.

Part I. The Production And Physical Properties Of High Frequency Currents

CHAPTER PAGE

I. The History of High Frequency Currents - 3

II. Sources of Electrical Energy - - 7

III. The Induction Coil - - - - 13

IV. Current Interrupters - - - - 21 V. The Alternating Current - - 36

VI. Static Machines - - - - - 43

VII. High Frequency Apparatus - - 46

VIII. The Physical Properties of High Frequency Currents :

(a) electro-static phenomena - - - 56 IX. Physical Properties — continued:

{b) DYNAMICAL PHENOMENA - - -62

(c) THE PHENOMENA OF INDUCTION - - 65

X. Physical Properties — continued:

(d) THE PHENOMENA OF RESONANCE - 67

(e) THE PHENOMENA OF ELECTRIC OSMOSE - 70

XI. The Application of High Frequency Currents:

(1) derivation - - - - - 72

(2) auto-conduction - - - - 75 XII. The Application of High Frequency Currents

— continued :

(3) CONDENSATION - - - - "79

(4) LOCAL APPLICATIONS - - - - 8 1

vii iriii CONTENTS

Part II. The Physiological Effects Of High Frequency Currents

CHAFTEK PAGE

I. Introductory - - - 87

II. The Effects of High Frequency Currents on

the Nervous System - - - - 94

III. The Effects of High Frequency Currents on

the Circulation - - - - 106

IV. The Effects of High Frequency Currents on

the Respiration - - - - 113 V. The Effects of High Frequency Currents on

Elimination - - - - -120

VI. The Effects of High Frequency Currents

upon Heat Production - - - 126

VII. The Effects of High Frequency Currents

upon Micro-organisms - - 132

Part III. The Therapeutical Uses Of High Frequency Currents

I. Introductory - - - - - 143 II. The Value of High Frequency Currents in

Certain Surgical Conditions - - 145

III. Tuberculosis - i - 148

IV. General Diseases - - - - - 158 V. Diseases of the Nervous System - 169

VI. Diseases of the Respiratory System - - 181

VII. Diseases of the Alimentary System - - 188

VIII. Diseases of Special Organs - - - 195

IX. Diseases of the Skin - 200

LIST OF ILLUSTRATIONS.

FIG. l'AGE

i. Hertz' Oscillator - - - - - 5

2. Primary Battery - - - - 8

3. Portable Accumulator (Secondary Battery) - 9

4. Lamp-Resistance Charging-Board - - - 10

5. Diagram of an Induction Coil - - 14

6. Intensified Induction Coil - - - - 16

7. Secondary Discharge from Intensified Induction

8. Diagram of Jointless Section-Winding - - 18

9. Induction Coil with Sparking Pillars - - 19

10. Platinum Interrupter - - - -22

11. Turbinia Jet Interrupter - - - 24

12. Autonome Interrupter - - - 25

13. Diagram of Autonome Interrupter - - 27

14. Mackenzie Davidson Interrupter - - 29

15. Dipper Interrupter - - - - - 30

16. Double-Dipper Interrupter - - - 31

17. Wehnelt Interrupter - - - - 32

18. Series Resistance - - - -33 i8a. Shunt Resistance - - 33

19. Switch and Resistance Board - - - 34

20. High-Tension Transformer - - - - 37

21. Alternating Continuous Motor Converter - 39

22. Nodon Valve - - - 40

23. Diagram of Nodon Valve - - - 41

24. Glass Plate Wimshurst Machine - - - 44

25. Ebonite Plate Wimshurst Machine - 45

26. Diagram of High Frequency Apparatus - - 47

LIST OF ILLUSTRATIONS

PAGE

27. Glass Plate Condensers - - 48

28. High Frequency Oil Condenser - - 49

29. D'Arsonval Resonator - - 51

30. Complete High Frequency Apparatus - 52

31. Roycourt High Frequency Apparatus - 54

32. High Frequency Milliamperemeter - - 55

33. Photograph showing the Effluve from the Top

of the Resonator, and Geissler Tubes lit up

by Induction - - - - 60

34. Direct Application - - - - - 73

35. Diagram of Experiment - - 74

36. Auto-Conduction Cage - - - 76

37. Horizontal Solenoid - - - - 77

38. Condensation - - 80

39. Diagram of Experiment - - - 80

40. Condensation Couch - - - - - 81

41. No. 1, Brush Electrode with Ebonite Handle;

No. 2, Spinal Electrode, of Ebonite, with Metal Core extending through the Stem and Crosspiece ; No. 3, Glass Electrode with Ebonite Handle ; No. 4, Thorax or Crescent

Electrode with Ebonite Handle - - 82

42. Vacuum Electrodes - - 83

43. Chaplin's Universal Holder and Electrodes - 83

44. Cataphoresis Electrode - - - - 84

Part I. The Production And Physical Properties Of High Frequency Currents

CONTENTS OF PART I.

I. The History of High Frequency Currents - 3

II. Sources of Electrical Energy - - - 7

III. The Induction Coil - - - - 13

IV. Current Interrupters - - - - 21 V. The Alternating Current - - - 36

VI. Static Machines - - - - - 43

VII. High Frequency Apparatus - - - 46 VIII. The Physical Properties of High Frequency Currents :

(a) electro-static phenomena - - - 56 IX. Physical Properties— continued:

(b) DYNAMICAL PHENOMENA - - - 62

(c) THE PHENOMENA OF INDUCTION - - 65

X. Physical Properties — continued:

(d) THE PHENOMENA OF RESONANCE - - 6j

(e) THE PHENOMENA OF ELECTRIC OSMOSE - 70

XI. The Application of High Frequency Currents :

(i) DERIVATION - - - - " 72

(2) AUTO-CONDUCTION - - - '75

XII. The Application of High Frequency Currents

— continued :

(3) CONDENSATION - - - "79

(4) LOCAL APPLICATIONS - - - - 8l

Chapter I. The History Of High Frequency Currents

High frequency currents may be denned as electric currents of a very high potential having oscillations of enormous frequency.

Professor Joseph Henry, of Washington, was the first to point out that the discharge from a Ley den jar is oscillatory in character.

If a charged condenser or a Leyden jar be discharged through a conductor of high resistance, the discharge increases in strength at first and then gradually dies away. If, however, the condenser be discharged through a conductor of low resistance, the discharge consists of a number of exceedingly rapid oscillations or surgings. This is caused by the self-induction of the circuit, by reason of which the current once set up tends to go on. The first rush more than empties the condenser, and charges it the opposite way; then follows a reverse discharge, which also overdoes the discharge, and charges the condenser the same way as at first, and so on.

Each successive oscillation is less than the preceding one, so that after a number of oscillations the discharge dies away.

^.arge is con-

Lord Kelvin, in 1853, showed that if

C be the capacity of the condenser,

R the resistance, and

L the co-efficient of self-induction, then if

R be greater than V ^- the disch tinuous, but if

R be less than \/ ^- the discharge is oscillatory.

In 1865 Maxwell put forward the electro -magnetic theory of light, which is that waves of light are not merely mechanical motions of the ether, but that they are electrical undulations. This theory, at the time, was without any experimental basis, but in 1888 Hertz succeeded in establishing the fact of a propagation of electric waves obeying the laws presented by Maxwell. Hertz employed to set up the waves an apparatus called an oscillator, consisting of two metal balls (A) insulated from each other, but nearly united by a metal rod, in the middle of which was interposed a spark-gap comprised of two metal knobs (B) with an intervening space.

The oscillator was connected with an induction coil (C). When a spark passes across the gap it sets up a temporary conducting path for the surgings to follow. Each spark set up by the coil across the gap consists of a number of oscillations, each lasting about y^ j^j q^-^ of a second, the period being determined by the capacity and self-induction of the apparatus.

The study of these oscillations has occupied the attention of a great number of scientists, but as regards the

THE HISTORY OF HIGH FREQUENCY CURRENTS 5 production, the study, and the utilization of high frequency currents we are mostly indebted to Hertz, Tesla, Thomson, and D'Arsonval.

In 1889 Joubert, using the apparatus of Hertz, previously described, found that the galvanoscopic foot of a frog did not respond to currents having an enormous number of oscillations per second.

In 1890 D'Arsonval showed that currents having a very high number of oscillations per second did not have any effect on either motor or sensory nerves.

(aWa)

FIG. I. — HERTZ' OSCILLATOR.

In 1891 Tesla demonstrated to the American Institute of Electrical Engineers his experiments on high frequency currents ; while devoting himself more particularly to the problems of electric lighting, and making use of the discharge from condensers, thus obtaining a very high frequency of alternations and a voltage equally high, he came to the same conclusions as D'Arsonval as to the physiological effects of the currents.

It was about this time that Elihu Thomson, using the discharge from condensers, greatly contributed to the simplification of the means of producing high frequency currents.

D'Arsonval then devised an apparatus which was suggested to him by the experiments of Sir Oliver Lodge on lightning conductors ; he connected the internal armatures of two Leyden jars with the terminals of the secondary circuit of an induction coil ; the external armatures were connected to one another by means of a spiral composed of about fifteen to twenty turns of a thick copper wire (the solenoid). To each internal armature a metal rod was attached terminating in a ball so placed as to form a spark-gap ; each time a spark crossed the spark-gap a current of a very high potential and a very high frequency of oscillations was set up in the solenoid, and could be collected from its two ends.

From this time D'Arsonval paid more attention to the therapeutical value of high frequency currents than to their physiological effects. Professor Bergonie, in his report to the Brussels Congress, states : "There is a name which will constantly be brought to our notice, but not so often as it deserves, in connection with this subject which would not exist if it were not for his work ; it is that of Professor D'Arsonval, of the Institute of France. He has one after the other invented the necessary instruments for producing high frequency currents ; he has formulated their physiological effects, and amply demonstrated their application in electro-therapeutics."

Chapter II. Sources Of Electrical Energy

In order to produce high frequency currents it is first necessary to consider from what source the electrical current is to be obtained, and secondly, how it is to be changed in character so as to enable it to be used to charge a condenser as described in Chapter I.

Electric-light mains may be used for this purpose, whether they are continuous or alternating, and are certainly the most convenient.

It is not possible, however, to obtain a main supply of electrical current everywhere, and under these circumstances either primary or secondary batteries must be used.

In the early days of electro -medical work primary batteries were employed, but by reason of the trouble they entail, their cumbersome size, the corrosive liquids they contain, the attention they need, their liability to breakage, and their small capacity, they have been practically abandoned. They are, however, useful where there is absolutely no other means of obtaining an electrical supply.

It is interesting to mention the construction and action of a primary battery. This consists essentially of two electrodes of dissimilar materials, immersed in a conducting solution of such a nature that chemical changes take place when the electrode's are so connected that an electrical current can pass through one to the other. In the bichromate cell a plate of zinc is one pole (the anode), while a pair of carbon plates, one on each side of the zinc and joined together at the top, constitutes the other pole (the

FIG. 2. — PRIMARY BATTERY.

cathode) ; these are immersed in a solution of sulphuric acid to which is added bichromate of potash, which acts as a depolarizer. This cell gives an electromotive force of about 2 volts.

The secondary battery cell consists of two plates of lead immersed in diluted sulphuric acid ; the acid should have a specific, gravity of 1*15 to 1*20. The sulphuric acid causes a thin layer of sulphate of lead to form on the plates ; if

SOURCES GF ELECTRICAL ENERGY 9

an electric current be sent through the cell, the sulphate of lead connected with the positive pole is changed to peroxide of lead, and bubbles of oxygen form, while the sulphate deposited on the plate connected with the negative pole is converted into spongy metallic lead, and hydrogen appears in bubbles.

FIG. 3. — PORTABLE ACCUMULATOR (SECONDARY BATTERY).

When the bubbles of oxygen and hydrogen rise to the surface and make the solution milky, the accumulator may be considered to be fully charged. If now the plates are connected to a conductor, an electric current will flow in the opposite direction to the current which previously charged the cell, and when the current ceases the plates will be found to have returned to their original condition.

io HIGH FREQUENCY CURRENTS

This process of charging and discharging may be repeated indefinitely.

It will be seen that the difference between primary and secondary batteries is that the former are charged by chemicals which have to be renewed when the cell is exhausted, while in the latter the current generates the chemicals, and when the cell is exhausted, or nearly so, the current will again regenerate the cell without any renewal of acid.

Continuous -current mains may be used to recharge accumulators, the current being passed first through a

1ST

FIG. 4. — LAMP-RESISTANCE CHARGING-BOARD.

number of lamps which serve as a resistance to control the current being passed into the accumulators. Great care must be taken that the main is connected in such a way that the current flows through the lamps to the positive pole of the accumulator, through the cells, and then out by the negative pole back to the main.

It will generally be found that when the cell has just been charged it will have an electromotive force of 2 to 2*5 volts; when the voltage falls below i'8 volts the cell should be at once recharged.

If an accumulator be not in constant use it should still be recharged from time to time and thus kept in working

SOURCES OF ELECTRICAL ENERGY u

order, as if it be allowed to run down sulphate of lead in a crystalline form is liable to be deposited on the plates, and this insoluble salt will so increase the internal resistance and decrease the storage capacity that the cells will be ruined.

An accumulator of ordinary size consists of 3 to 6 cells, giving a total pressure of from 6 to 12 volts, according to the number of cells.

Accumulators are now made in a very much more portable form than hitherto, which is an important consideration when they have to be taken any distance to be charged. The advent of the motor-car and the need for portable cells has produced this, and it is now possible to obtain from many of the leading accumulator-makers a very neat and compact form of accumulator, the plates being enclosed in a transparent celluloid cell. By this arrangement there is no danger of the acid being spilt, and the plates may be examined during the process of recharging.

Great care should be exercised in selecting accumulators, and only reliable and well-known makers should be dealt with. The Electrical Power Storage Company make a most convenient and efficient portable accumulator.

If it be not possible to have the accumulators charged at a generating station, a small gas or oil engine is necessary in order to drive a dynamo which will produce an electrical current for the purpose of charging the accumulators.

Where there are electric-light mains in the neighbourhood a supply of electricity can be obtained direct. There are two kinds of electric current supplied by corporations and companies for public consumption — one is the direct or continuous current, the other is the indirect or alternating current. When currents from the main are employed, it is necessary to know whether the current is continuous or alternating, what the voltage is, and, should the current be alternating, the periodicity or frequency of the alternations.

The difference between the direct or continuous current, and the indirect or alternating current, is that in the former the flow of current is always in one direction and practically at a uniform voltage or pressure, while in the latter the current flows first in one direction and then in the other, with a constant change of polarity, and rises and falls in pressure from maximum to minimum, the alternations or cycles varying from 40 to 100 per second.

The direct-current mains have a voltage varying from 100 volts and upwards. A pressure of 100 volts is the most suitable for ordinary purposes, but of late the electric supply companies have increased their pressure to from 200 to 250 volts, in order to enable the conductors to carry more energy without the necessity of increasing their sectional area, thus saving a considerable amount of capital outlay on copper for the mains.

Chapter III. The Induction Coil

An electrical supply obtained either from the electric-light main or from accumulators is of comparatively low tension or voltage (the terms are synonymous), and before it can be utilized for the production of high frequency currents the ratio between pressure and current must be altered.

There are several methods of accomplishing this according to the local conditions and facilities. One way of effecting this transformation is by means of an instrument known as the induction coil, which is applicable principally for use in conjunction with continuous-current mains or with accumulators. It is generally known that when an electrical current is passed through a wire wound round a bar of soft iron the latter is magnetized, and when the current is broken demagnetization immediately results.

This is one of the fundamental principles of an induction coil which consists essentially of four parts — namely, the core (A), the primary winding (B), secondary (C), and condenser (E).

The core in an induction coil represents the iron bar, and the wire wound round it the primary.

The core of an induction coil, however, does not consist of a bar of iron, but of a number of strips of soft iron of good quality carefully annealed and bound tightly together with paraffin tape. Strips of soft iron are used in preference to a bar, as demagnetization is more spontaneous in the former, due to the absence of hysteresis and Foucault currents.

FIG. 5.— DIAGRAM OF AN INDUCTION COIL.

On the outside of the core the primary is wound, consisting of several layers of insulated wire of high conductivity.

In the latest types of coils the primary is subdivided and arranged so that the different layers may be connected in series, series parallel, or parallel, according to

THE INDUCTION COIL 15

the character of electrical current and the method used to break the current in the primary. The core and primary are both enclosed in a stout ebonite or mica tube.

On the outside of the primary, but insulated from it, is wound the secondary, which consists of a great number of turns of fine wire carefully insulated. The quantity of wire used to form a secondary varies according to the size of the coil, but it may be of interest to note that a coil of such a size as to produce a 10-inch spark requires about twenty miles of wire.

In the older type of coils it was usual to wind the secondary right along the length of the coil ; in the improved constructions, however, the secondary is wound in what is known as " multiple section " — that is to say, the wire is wound in a series of wheels or discs, which are placed side by side and separated by a thin sheet of insulating material.

In a coil giving a 10-inch spark there are about seventy to eighty of these sections, the whole being very carefully insulated in paraffin wax and enclosed in an ebonite cover.

Referring to the action of the coil again, the effect of the rapid magnetization and demagnetization of the core is to produce lines of force which circulate round the secondary winding, causing induced currents in the latter which are of very high tension.

Reference has not yet been made to the condenser, the principal function of which is to hasten the elimination of the current from the primary, for much of the efficiency i6 of the coil depends upon the rapidity at which this is accomplished.

e-iii^i

OS3

When the current in the primary is broken, the spark at the point of contact is liable to lengthen the time

THE INDUCTION COIL during which the current can pass, and the process, instead of being a rapid one, is liable to become protracted. The condenser has also the effect of reducing the sparking at the point of contact, as it receives the E.M.F. induced in the primary, caused by the breaking of the circuit.

The condenser consists essentially of a number of sheets

FIG. 7.— SECONDARY DISCHARGE FROM INTENSIFIED INDUCTION COIL.

of tinfoil separated by waxed paper, every alternate sheet of foil being connected together, and the two sets formed in this manner connected to either side of the current interrupter.

A complete coil of the most recent construction is shown in Fig. 6. The tube enclosing the core and primary projects from either end ; the large diameter central portion contains the secondary with the two connecting terminals. The condenser is contained in the base, and the plugs for varying the arrangement of the primary are shown, one in position and three lying in front.

Induction coils are made in various dimensions, their size being gauged by the length of secondary discharge which it is possible to obtain from them. The length of

FIG. 8. — DIAGRAM OF JOINTLESS SECTION-WINDING.

the secondary discharge is, of course, proportionate to the size of the primary, secondary winding, etc.

For practical high frequency work a coil capable of producing a secondary discharge of at least io-inch sparklength is required. Coils giving a much longer spark are advocated by some workers on account of the increased output it is possible to obtain from them. When selecting a coil, consideration must be taken not only of the length of the spark, but of its thickness. A good coil will give

THE INDUCTION COIL a thick, furry spark which will exceed its nominal sparklength by about 10 per cent.

A new type of induction coil is shown in the illustration on p. 16. This particular coil is known as the Intensified Induction Coil, and the principal advantage claimed for it is the greatly increased capacity of the high-tension impulses compared with other forms of induction coils. This result is obtained by a very careful and exact

FIG. 9.— INDUCTION COIL WITH SPARKING PILLARS.

measurement of the various qualities of the materials used in its construction. The coil is made only in one size, with the secondary terminals separated by 12 inches, although, so great is the output, it is possible to obtain a discharge varying from 16 to 18 inches in length.

An estimation of the heavy secondary discharge can be gained by Fig. 7, which is an actual photograph of a discharge obtained from one of these coils.

Another good type of induction coil is made on the multi-section principle, but with the sections wound in

2 — 2 one continuous length of wire, without the usual jointing between each section. These coils are designated "jointless section " (Fig. 8), and, on account of the reduced resistance and impedance due to paper insulation instead of the usual wax, produce a heavy secondary discharge.

Chapter IV. Current Interrupters

Having described the function and construction of the induction coil, the next instrument to consider is that used for interrupting the current in the primary. Too much importance cannot be attached to this instrument, for upon it depends much of the satisfactory working of the apparatus.

The various forms of current interrupters, or contact-breakers, as they are sometimes called, which commend themselves to the worker may be roughly divided into three classes, namely :

The platinum or hammer interrupter.

The motor mercury interrupter.

The electrolytic interrupter.

Describing the different forms of contact-breakers in the above order, the first may be quickly passed over, as it is not altogether adapted for high frequency work. It is one of the oldest forms of current interrupters, probably the oldest, and was used almost universally some years ago, when coils of any size were first used by medical men for the production of high-tension impulses.

The platinum interrupter consists of two platinum points mounted on springs in such a way on the base of the coil facing the core, that when the current is passed they are separated and brought together by magnetic attraction. Fig. 10 shows a diagram of a very good form of one of these interrupters. The effect of passing the

FIG. IO. — PLATINUM INTERRUPTER.

current into the primary is to pull the hammer of the interrupter towards the coil, breaking the circuit between the two platinum points at F. Immediately the current is broken demagnetization of the core results, and the spring carrying the hammer comes back into its original position, when the same process repeats itself.

It will be seen that the speed of make and break is controlled by means of the adjusting screw D. Tension may be placed on the spring B by means of the milled head A, with the effect that a stronger current is required in the primary to effect a sufficiently strong attraction to separate the platinum points.

On account of the simplicity of the platinum interrupters, and the comparatively small space occupied by them, they are useful in portable apparatus. They are, however, not very suitable, as previously mentioned, for use with high frequency currents, as the speed of interruptions with the majority of forms is not rapid enough, nor is the break sufficiently steady.

Platinum interrupters 'are best worked from a low pressure of 10 to 16 volts, such as is usually obtained from accumulators.

The motor mercury interrupter for high frequency work is without doubt the most efficient and best allround contact-breaker. The break consists of two parts — viz., (1) an arrangement for making and breaking the contact between a bath or jet of mercury connected to one pole and a contact connected to the other pole ; (2) a motor to supply the power to make and break the current.

It is obvious that by varying the speed of the motor the number of interruptions in the primary circuit can be increased and decreased as desired. The majority of forms of mercury interrupters have the advantage that they will work either from accumulators or from a main supply. There are a number of different forms of mercury interrupters, all of which are more or less efficient.

The mercury jet interrupter, as illustrated in Fig. u, as its name implies, consists of a jet of mercury which is produced by means of a centrifugal pump, and impinged against wedge-shaped blades revolving at a high speed. The height of the jet of mercury in relation to the blades is adjustable, and by means of this the time and duration of contact can be altered by racking the jet

FIG. II. — TURBINIA JET INTERRUPTER.

up and down. This is of great importance, as with a long period of contact more current can pass than with a short period. In this manner it is possible to adjust to a nicety the quantity of current passing into the primary of the coil, and the consequent effect obtained at the secondary.

The jet interrupter will work equally well on a low voltage (obtained from accumulators), or from highpressure electric-light mains, and the currrent which it consumes is comparatively small.

Another advantage with this form of interrupter is that it is impossible for a short circuit to take place in the primary of the coil, as, should the motor inadvertently

B

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h* C

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FIG. 12. — AUTONOME INTERRUPTER.