Medical electricity; a practical treatise on the applications of electricity to medicine and surgery

Front matter

.■ng/qAAiAAl (h

I$J% iXM

TRANSFERRED TO YALE MEDICAL LIBRARY

Preface To The Second Edition

As a considerable edition of this treatise was exhausted within a year, and the demand continuing unabated, I feel that I did not misconceive the need of the time for a practical work on Medical Electricity. My purpose was to prepare a work from the practitioner's, rather than the merely scientific, standpoint. In the present edition the same conception of the subject continues paramount ; and in that spirit, I have made many additions and improvements to render the work more useful to those for whom it is intended. At the same time, in response to what seems to me an increasing desire for scientific treatment, I have developed more fully the modern methods of ascertaining and expressing current strength, tension, resistances, etc. I have, also, entered more fully into the polar method, and into the action and uses of the magnet. Notwithstanding an increase in the number of lines to the page, and the condensation of the matter new and old, the work has been enlarged by the addition of thirty pages. Thus improved, I may be permitted to hope that the new edition will continue to enjoy the favor so largely bestowed on the first.

Roberts Bartholow.

Philadelphia, 1509 Walnut Street.

Preface To The First Edition

In my annual course of Lectures on Materia Medica and Therapeutics, I have discussed, more or less fully, the subject of electricity as a therapeutic agent. It happened in this- way that my attention was called to the need of a suitable text-book. That there are excellent works on medical electricity is undeniable ; but some of them are too voluminous, others too scientific, and not a few wanting both in fulness and in accuracy. I have attempted in the preparation of this work to avoid these errors ; to prepare one so simple in statement, that a student without previous acquaintance with the subject may readily master the essentials ; so complete as to embrace the whole subject of medical electricity, and so condensed as to be contained in a moderate compass. I have endeavored to keep constantly in view the needs of the two classes for whom the work is prepared— students and practitioners. I have assumed an entire unacquaintance with the elements of the subject as the point of departure — for I am addressing those who have either failed to acquire this preliminary knowledge, or having acquired it, find that after the lapse of years it has become misty and confused.

In the account of electrical phenomena, I have adhered to the modes of expression with which the medical electrical text-books have made us familiar. The time has not come, it seems to me, to adopt the terms and explanations now employed by practical electricians : it is a transition period in which both the old and the new should have a measure of recognition. I have, accordingly, followed the usual course in the account of electrical principles and instruments, introducing also the new terms — the units — by which the electro-motive force, quantity, capacity, and resistance are expressed. Electricity as applied to practical arts — to lighting, heating, telegraphy, and mechanical work generally — demands different treatment, especially as

Vlll PREFACE.

respects the means and methods of exact measurement, from that required in the presentation of its medical uses. Although it is true that exacter methods of stating current strength, resistances, etc., are desirable in the medical applications of electricity, we are not yet in a position to avail us of the results achieved in the applied science, for the human body is an altogether more uncertain quantity than a copper wire of given length and sectional area. Furthermore, a proper statement of the various questions in the electrical science of to-day, requires the use of the higher algebra and the calculus — an amount of mathematical knowledge not universally possessed by medical students and practitioners. I have, however, entered somewhat into the consideration of the polar method, especially as developed by Erb and Brenner, and have described the mode in which the reactions are now expressed. An entirely novel subject is the adaptation of the Toepler-Holtz electrical machine, by simply connecting the interior and outer coating of the condensers, for the production of nerve and muscle reactions just like those of the primary faradic current. I know of no publication in which this novel fact has been stated. 1 It accordingly opens up for the first time an important field for future investigation and research.

This book, then, must be regarded as the exposition of electricity for remedial purposes, made by a medical practitioner for the use of other medical practitioners. No claim is made on the ground of pure science. It is believed, however, that the work makes an adequate presentation of the subject, regarding electricity as a remedial agent — as one of the means employed for the treatment and cure of disease.

Roberts Bartholow.

Philadelphia, 1509 Walnut Street, March, 1881.

1 As this work is going through the press, my attention is called to a paper by Dr. W. J. Morton in the New York Medical Record for April 9.

Contents

PAGE

Introduction, . . . . . . . . 17

Modes of the force, . . . . . . -17

Chapter I. Magnetism

Magnets,

Natural,

Artificial, Lode-stone, North polarity, South polarity, Law of polarity, Magnetic bodies, Diamagnetic bodies, Magnetic induction, Forms of magnets, Coercitive force, Magnetic inclination, Magnetic declination,

21 21 21 22 22 22 23 2 3 24

25 26 27

CONTENTS.

Chapter II. Static Electricity

Static, frictional, or Franklinic,

Vitreous,

Resinous,

Theory of Dufay,

Conductors, .

Insulators,

Induction,

Electrical machines,

Leyden jar, .

Battery of Leyden jars,

Potential,

CHAPTER III. Galvanism, Voltaic electricity

Galvanic element,

Generating plate,

Conducting plate, Conjunctive wire, .

Galvanometer,

Astatic, .

Positive and negative currents, Volume of the current, .

Direction of the current, Intensity, Resistance, Ohm's law, Unit of resistance, Unit of intensity, .

The Ohm, The Weber, .

The Farad, Measurement of current strength, Measures of capacity,

XI

PAGE

The voltameter,

The rheostat,

Water, .

Wire,

.

Processes of galvanic discharge,

Discharge by conduction,

• 45

By disruption,

. 46

By convection

. 46

. 46

Cathode,

Anions,

• 47

Cations,

Chapter IV. Forms

OF GALVANIC COMBINATIONS

Single fluid battery,

.

Smee's element,

Grenet's element, .

Stohrer's battery, .

.

5°

Grove's

.

Daniell's "

5 2

Siemens and Halske's battery,

Hill's gravity battery,

Leclanche's element,

Permanent batteries,

Arrangement of cells,

Portable batteries, .

Key or pole board,

Resistance coils,

Cabinet battery,

Remak's battery, .

•

Chapter VIII. Care Of Batteries, Galvanic And Faradic I Manipulation

The apparatus, ......... 86

How to detect faults, ........ 88

Current strength, ......... 88

The poles, 88

Moistened electrodes, ........ 90

Dry electrodes, ......... 90

Stabile and labile, ......... 90

Direct or descending, . . . . . . . -91

Inverse or ascending, 91

CONTENTS.

Xlll

General electrization, ... ... 91

Electric bath, .... ... 91

Derived currents, . . . . . . . . -92

Chapter V. Action Of Galvanic And Faradic Electricity On Muscle

STRIATED AND NON-STRIATED.

Action of galvanic current on muscle, . . . 113

Galvano-tonic contractions, . . . . . . .114

Action of faradic current on muscle, . . . . .115

The polar method, . . . . . . . 115

The normal formulae, . . . . . . . .116

Action of galvanism on non-striated muscles, . . . .117

Part IV. Electro-therapeutics

CHAPTER I.

MAGNETO-THERAPY — THE THERAPEUTICAL APPLICATIONS OF THE

MAGNET.

History, 145

Physiological effects of the magnet, 146

Therapeutical applications, 149

Neuralgia, . 15°

Chorea, 15°

Hemianaesthesia, 150

XVI

CONTENTS.

CHAPTER II.

STATIC ELECTRICITY ITS METHODS AND USES.

History, ....

Appliances of static electricity,

The Toepler-Holtz machine,

The electric bath, Nerve and muscle effects, Therapeutical applications,

Neuralgia,

Hystero-epilepsy,

Paralysis,

Chorea,

*59 160 160 160 161 161

Chapter III. Electricity In Cerebral Affections

Cerebral congestion, ........ 162

Psychical affections, . . . . . . . .166

How to apply the electrodes, . . . . . .168

Chapter IV. Electricity In Spasm And Cramp

Histrionic spasm, . . . . . . . . .170

Blepharospasm, . . . . . . . . -171

Stricture of oesophagus, . . . . . . . .172

Spasmodic asthma, . . . . . . . . -173

CONTENTS.

XV11

Chapter V. Electricity In The Paralyses

Spinal paralyses, ....

• 177

Paraplegia,

Chronic myelitis,

Infantile paralysis, ...

Pseudo-hypertrophic,

Progressive muscular atrophy, .

Sclerosis of the cord,

. 189

Peripheral paralysis,

Facial paralysis,

Muscular paralysis, ...

Paralysis of ocular muscles,

Hysterical paralyses,

Diphtheritic paralysis,

Lead paralysis, ... . .

Chapter X. Electricity In Local, Other Than Nervous Diseases

Naso-pharyngeal catarrh,

Vomiting,

Atonic dyspepsia, .

Constipation,

Impaction of the intestines,

Respiratory depression, .

Cardiac depression,

Uterine hemorrhage,

Amenorrhoea,

Irritability of the bladder,

Impotence,

Genital irritation, .

Urethral applications,

Electrodes for various uses,

2 39

240 240 241 232 243

CONTENTS.

XIX

Index, .

284 287 289

A TREATISE

MEDICAL ELECTRICITY.

Introduction

MODES OF THE FORCE.

Electricity is one of the physical forces — a mode of manifestation of energy, kinetic and potential — and is convertible into or is correlated with the other modes of force. It is manifested in several forms; as —

Magnetism.

Static Electricity:

Vitreous,

Resinous.

Dynamic Electricity:

Galvanism,

Faradism :

Electro-magnetism, Magneto-electricity.

Thermo-electricity.

Magnetism differs from the other modes of electrical force in that the energy of the excited body is always present. The pieces of magnetic iron ore, or of steel in which the magnetic property has been induced, are always in a condition to exhibit their special powers;

18 INTRODUCTION.

i. e., suspended and free to move, always assuming a uniform direction, or attracting certain bodies in their neighborhood. Static electricity is developed from a material — glass or resin — which is entirely quiescent until excited by friction. Galvanism is produced by chemical action or by contact which causes electrical separation, and faradism is the result of induction by galvanism. When friction or chemical action ceases, the resulting phenomena subside.

Medical electricity is the application of the science of electricity to the requirements of medical practice, and is concerned with all of these modes or manifestations of electrical energy.

There are certain terms now employed in giving mathematical expression to the facts of physical science, and some knowledge of them is therefore necessary in the study of electricity.

Matter and force are terms in frequent use. From the point of view of physics, matter is a something by and through which the forces act. Force is defined to be that which can change any body's state of rest or motion. The unit of force is called a dyne.

The unit of mass is a cubic centimetre of distilled water at 4 Cent. This mass is the gramme, and on it is based the decimal system.

Work is defined as overcoming resistance through space. When a weight is raised, work is done in overcoming the force of gravity through the space over which the weight is moved. The English unit of work is the foot-pound — that is, the work done in raising one pound one foot in height. The Continental unit of work, called the Erg, is the work done in moving a gramme, through the space of a centimetre, against a unit of acceleration.

Energy is the capacity for doing work, and may be

INTRODUCTION. 19

kinetic, when the body employed is in actual motion, or it may be potential, when it has the power to do work, or is in a condition that work may be recovered from it. Thus, when a spring is bent, or weight raised, and is in a position to act, potential energy is acquired by the work done in bending the spring or in raising the weight. Potential becomes actual or kinetic energy when the spring or weight is released to move some other body, or to do work of some kind.

Difference of potential between any two points is the work done in carrying a unit of mass from one point to the other. Zero potential is the point chosen as a standard of reference. Any place which requires work to be done to bring the unit of mass from the zero point to it will have positive potential, and any place which requires work to be done to bring the unit of mass from it to the zero point has negative potential.

Part I. Electro-physics

CHAPTER I.

MAGNETISM.

The term "magnet" was originally applied to certain iron ores possessing peculiar properties, and which were found near the ancient city of Magnesia, in Asia Minor. In one respect this native ore differed from all others: it had the power of attracting to itself other small particles of iron. It was subsequently discovered that the property possessed by some natural iron ores could be communicated, under certain conditions, to other pieces of iron ; whence the distinction into natural 'and artificial magnets. The natural magnet is also called lode-stone, or, more properly, lead-stone, because of the power it possesses of drawing, or leading to motion, certain substances subjected to its influence. If a permanent magnet be made to approach a bar of soft iron, suspended at its centre and free to move, the bar is attracted and moves toward either end of the magnet. If now a bar-magnet is substituted for the soft iron, and suspended to move freely, when another permanent magnet is made to approach, it is found that, whilst one extremity of each is attracted, the other extremities are not attracted — are, on the contrary, repelled, and they cannot be made to approximate to each

Fig. i.

other. Moreover, we observe that the suspended magnet left to itself invariably assumes a certain position. If disturbed, after a period of oscillations, it finally settles to rest in the one position — one extremity pointing to the north, the other to the south. Further investigations demonstrate that the peculiar properties of the magnet reside only in the extremities, and that they disappear at the centre, which is hence known as the neutral point or magnetic equator, etc. These a permanent magnet. extremities of the magnet are termed poles, and the property exhibited by them is called polarity (Fig. i). That extremity of the magnet which points to the north is called the north pole — or the marked extremity, because it always contains a mark to designate it; the other end is called the south pole. If we bring the north pole of one permanent magnet into the neighborhood of the south pole of another permanent magnet, they immediately attract each other and strongly adhere, so that some force is required to separate them. On the other hand, if we approximate the north or the south poles of the two magnets, they manifest a mutual repugnance and fly from each other. Hence the law: Like poles repel, unlike poles attract.

Not all bodies are affected by a magnet in their neighborhood. Some are attracted; others are repelled; the former were entitled by Faraday magnetic— the latter diamagnetic. No substance is so strongly affected by a magnet as iron. The following is a list of the more important of the two groups:

MAGNETISM. 23

Magnetic. Diamagnetic-

Iron, Bismuth,

Nickel, Antimony,

Cobalt, • Zinc,

Manganese, Tin,

Platinum, Mercury,

Osmium, Lead,

Palladium, etc. Silver,

Copper, Gold, Arsenic, etc.

The substances in the list of magnetic bodies are not affected to the same extent, yet they are all attracted in the same way. If a needle or small iron bar is suspended between the poles of a powerful permanent magnet, so made that the north and south poles are exactly opposite each other, it assumes a position in a plane parallel to a line drawn from one pole to the other — an axial position. Whence we deduce the law: A magnetic body suspended between the poles of a magnet assumes an axial position.

If a diamagnetic substance — a piece of bismuth, for example — be suspended in the same way between the poles of a permanent magnet, it takes a position not axial, but at a right angle to axial — an equatorial position. Whence we deduce the law: A diamagnetic substance suspended between the poles of a magnet assumes an eqziatorial position.

Very different results are obtained when the body suspended between the poles of the magnet is at the same time immersed in a magnetic liquid instead of air. This point is well illustrated by suspending mica, a magnetic substance, in a solution of protochloride of iron, which is more magnetic. Under these circumstances the mica will not follow the same law as when suspended free in the air, and will instead assume an equatorial position. As the same results follow the same mode of treatment of other magnetic substances, we deduce the following law: A magnetic substance suspended in a fluid more magnetic than itself will assume the position of a diamagnctic substance. It is found that the converse is true, also — whence the law: A diamagnetic substance suspended in a liquid more diamagnetic than itself tuill assume the position of a magnetic substance.

It has been already pointed out that like poles repel and unlike poles attract. The influence of one magnet on another is also exhibited before they are actually in contact — even when a considerable space intervenes — but it is the more powerful the nearer they approximate to each other. This influence is expressed by this law: The magnetic foi'ce is exerted inversely as the square of the distance. When a permanent magnet is made to approach a bar of soft iron, the latter is attracted, because the opposite polarity is diverted to that extremity of the iron nearest the magnet. In this fact we have an exhibition of the phenomena of induction. Magnetism is a force existing in the bodies capable of its manifestations, under ordinary circumstances in a quiescent state. When the magnet is brought near to the bar of soft iron, the neutral magnetic condition of the iron is disturbed, and it assumes a polar state, north polarity magnetism accumulating at one extremity, and south polarity magnetism at the other. When the permanent magnet is withdrawn, these evidences of polarity cease, and the magnetism in the bar of soft iron resumes its neutral or unexcited condition. By the approach of the north or marked pole of the magnet, the opposite magnetism (or south) is induced at the extremity of the bar nearest the magnet. Similar phenomena occur in static electricity —

MAGNETISM.

for example, when the excited electric approaches the suspended pith-ball. The production of two instantaneous currents in a coil of fine wire, about the conjunctive wire of the galvanic battery is another example of the principle of induction.

When a permanent magnet is broken into two pieces, each is found to possess north and south polarity; and if these two pieces are broken into others, each remnant is found to be a complete magnet. The subdivision may

Forms of horseshoe magnets.

be carried on still further with the same effect. This result is explained by supposing that each separate molecule of iron is endowed with the two magnetisms — with north and south polarity.

Magnets are made in the form of a bar, or of a needle, and of a horseshoe, the magnetic property being the same in either case (Fig. 2). In the preparation of a magnet the hardest steel is used. It ought to be so hard as not to be attacked by a good file. Steel is employed for this purpose, and the hardest steel, because it possesses in a higher degree than ordinary iron the coercitive force — or the power to retain the magnetic property after it has been imparted to it. In the process of magnetizing a steel bar, the single or double touch may be employed. By the single touch, over that extremity which is intended to have north polarity, the south pole of a magnet is rubbed, beginning at the centre of the bar and stroking it outwardly, and coming back to the point of starting, through the air. The other extremity of the steel bar is treated in the same way with the north pole of the magnet. The double touch consists in applying two magnets, at an angle of 15 to 20 with the bar, beginning at the centre and stroking both extremities simultaneously. Certain precautions are necessary to preserve the activity of magnets. The poles, both of the straight and horseshoe form, should be connected by a bar of soft iron. Notwithstanding steel possesses in a high degree the coercitive force, the magnetic property may be easily destroyed. A blow, scratching the surface, rubbing with any hard substance, especially heating the magnet, injure its magnetic effect. It is injurious to lay the magnet on iron.

When a magnet is suspended or balanced on a pivot and free to move in any direction, it assumes, as has been stated, the position of north and south polarity (Fig. 1). When a magnetic body is suspended between the poles of a permanent magnet, it assumes an axial position. The earth is a great magnet, having its southern pole in the neighborhood of the geographical north pole; consequently, the north pole of the magnet is attracted toward the north — unlike poles attract. It is this remarkable property which renders the needle of the compass so important to mariners.

The needle does not always point due north. The angle which the north pole of the needle makes with a horizontal plane is called the "Dip" or "Inclination," and the angle which it makes with a vertical plane due north from the centre of the needle is called the "Declination." At the equator, the needle is nearly horizontal, but as either pole of the earth is approached, it dips until at certain points it stands vertical. The declination of the needle from 1580 to 1657 was easterly in London, and from 1657 to 18 1 5 was westerly, and since the last-mentioned date has been going easterly again toward the astronomical meridian. From the time of the discovery of the inclination of the needle up to 1723 the inclination increased ; from that time to the present it has decreased. There seems to be a decennial period in the more considerable disturbances of the declination, and are apparently determined by the sun spots. There are oscillations diurnal, lunar, etc.

CHAPTER II.

STATIC ELECTRICITY.

Static, frictional, and Franklinic are the terms applied to this force. It is static, because the electricity is restrained in a condition of high tension ; it is frictional, because developed by friction of certain substances, as glass and resin; and it is Franklinic, because Franklin demonstrated the identity of frictional with terrestrial electricity. The phenomena of static electricity are illustrated by simple means. If a glass rod is rubbed with a silk handkerchief, it is found to possess a new property.

That portion of the rod subjected to friction, if approached near a pith-ball suspended by a silk thread, attracts it, and after a short time in contact with the rod the ball is repelled. The friction develops electricity, the particles of which are self-repellant, since as soon as the pith-ball is charged it is continually repelled by the glass rod. This is called vitreous electricity, because obtained by the friction of glass. If now a piece of resin be rubbed with flannel, and brought near to the charged pith-ball, the latter will be at once attracted. After a time becoming charged with electricity from the resin, the pith-ball will be repelled, and whenever approached by the excited resin so long as it is charged by its electricity, repulsion will occur. We learn from this experiment that there is another form of electricity — the resinous, and that the particles of this are also self-repellant. If we reverse this experiment, and charge the pith-ball first with resinous electricity, we find that the ball is presently repelled, and that when in this condition, an excited glass rod is brought near it, the ball is at once attracted. It is clear, therefore, that the two electricities attract. From these observations we deduce the law: Unlike electricities attract, like electricitiesrepel '(Fig. 3) .

Fig. 3.

Unlike electricities attract — like, repel.

According to the theory of Dufay, which is now generally held, there are two electrical fluids — the positive and the negative, or vitreous and resinous. These are generally distributed, mixed together, neutralizing each other, and perfectly quiescent, when so united. By certain processes — friction, chemical action, motion, heat, etc. — a separation of the two electricities takes place, but there must be present just as much of the one as of the other. In rubbing the glass rod, the glass is excited positively, but the silk is excited in the same proportion, by negative electricity. These two forms of electricity are called respectively "positive" and "negative," and the signs + and — are used to designate them, the + sign being arbitrarily applied to vitreous electricity.

With regard to electrical action bodies are divided into two great groups, conductors and insulators. They may be arranged as follows: —

Conductors. Insulators.

Metals, Caoutchouc,

Charcoal, Silk,

Graphite, Glass,

Acids, Wax,

Water, etc. Sulphur,

Resins, Shellac, etc.

This sharp division into two groups is not always possible. In some instances, conductors of the least perfect kind become insulators; and poor insulators become tolerable conductors. The very best conductor offers some resistance to the passage of the current. Circumstances affect the position of these bodies. Dry air is a non-conductor, but if moisture is present it becomes a conductor. Glass is a non-conductor in the ordinary state, but when heated to redness, becomes a good conductor. A conductor is said to be insulated when mounted on some non-conductor or insulator. For example, a brass rod mounted on glass or caoutchouc is insulated. Without insulators, electricity could not be collected to exhibit the various phenomena of which this force is capable.

Electricity is not only transmitted by conduction, but it operates through the intervening molecules of air, by induction. Thus, if an excited glass rod is brought near to the gold-leaf electrometer, the leaves diverge. There is no conduction; the rod is not in contact with the brass knob of the electrometer, but the gold leaves separate as soon as the rod approaches, so that an influence of some kind is exerted through the air. When the excited glass rod approaches suspended pith-balls, they move towards the rod, for, on that side of the balls nearest the rod, the opposite or resinous electricity accumulates, whilst the vitreous flows to the other side. In other words, the excited glass rod induces the opposite, or negative, or resinous electricity on the side of the pith-balls nearest it. As in accordance with the law, unlike electricities attract, the pith-balls fly and attach themselves to the rod, until charged with vitreous electricity, when they are repelled.

Electricity accumulates upon the surface of bodies, and not in their interior. This fact is demonstrated by the following experiment: A solid sphere of brass, resting on a glass stand, is covered by two accurately fitting hemispheres of brass. Putting these hemispheres in position on the globe, they are charged with electricity. On removing the hemispheres, they are found to contain the whole charge, whilst the globe itself presents no evidence of the presence of electricity, showing that the electricity only diffuses itself on the surface. The form of the body receiving a charge greatly influences the distribution of the electricity. If a sphere be charged with positive electricity, and then be made to approach another sphere not charged, the neutral electricity of the latter is decomposed, negative electricity accumulates on the side nearest the excited sphere, and positive on the other side (Fig. 4). If, instead of a sphere, a cylinder be charged, and brought

STATIC ELECTRICITY.

near an unexcited cylinder, the electricity accumulates at the extremities, and the phenomena of polarity are exhibited.

Fig.

Electrical induction.

Certain substances without having the power to conduct electricity allow it to pass through them — in other

Fig. 5.

A plate-glass electrical machine.

words, they are transparent to electricity, as glass is to light. Such substances are said to be dialectric. If electricity be excited on one side of a plate of glass, the other side will exhibit electrical phenomena.

To obtain a large quantity of electricity, other means than friction of glass rods or sticks of resin become necessary. Two kinds of electrical machines are used —the cylinder and plate glass (Fig. 5). The glass is subjected to friction by rubbers, and the electricity is collected by brass points and conveyed to a reservoir — the prime conductor (Fig. 6). The rubber becomes

Fig. 6.

A cylinder electrical machine.

negatively and the glass positively electrified. In the Holtz machine (Fig. 7), the principle of induction is utilized. This machine consists of two circular upright glass or hard rubber plates placed very near each other, without touching, one arranged to revolve, whilst the other is fixed. The fixed plate has a central orifice, through which the axis of the other plate passes, and has on its outer surface some oblong pieces of parchment paper. In front of the revolving plate is a brass rod, containing at each extremity some projecting points or combs, and is fastened at the centre by a pivot. At the border of the fixed plate there are metallic combs, fastened on by rubber rods. There are two condensers

STATIC ELECTRICITY.

(Leyden jars), connected in their interior by brass rods, which communicate with the discharging rods; and their exterior coating is connected by a brass rod passing under the wooden base. The fixed glass plate of the original Holtz machine had windows, through which paper points projected against the revolving plate. In the Toepler-Holtz, these windows are dispensed with, and soft wire brushes are so adjusted in front, as to rub against brass knobs fixed in the revolving plate. To

Fig. 7.

The Toepler-Holtz electrical machine.

start this machine, it is necessary, only, to place the discharging rods in apposition, and cause the revolving plate to move. When the current passes, the discharging rods are separated, and a stream of sparks flows from one to the other.