Medical Jurisprudence, Forensic medicine and Toxicology. Vol. 1

by R. A. Witthaus; Tracy C. Becker

RESULTS OF ACCIDENTS AND INJURIES FROM ELECTRICAL MACHINES AND CONDUCTORS.

Medical Electricity.—In the ordinary use of the mild forms of electricity employed for medical purposes, certain phenomena may at times occur, which, although not of any serious import or of long duration, may yet cause considerable inconvenience, pain, or discomfort to the patient or others, and may even be of some importance from a medico-legal point of view. We shall not enter here into the discussion of the proper methods of application of medical electricity, nor do more than point out that if these be not followed with care the patient may be not only not benefited, but made worse, and may even suffer considerable injury. The increase of pain caused by the improper application of certain currents is usually temporary and of minor consequence. But serious and lasting inflammations may be caused by the careless, ignorant, or injudicious use of the stronger currents internally, and metritis and peri-uterine inflammations have been not infrequently reported from the unskilled practice of the methods of Apostoli. These subjects, however, scarcely come under the scope of this article.

In addition, however, to these troubles we may have external injuries produced. Even in cases where the current amounts to not more than a few milliamperes burns may be caused by the ordinary electrodes of the galvanic battery. The faradic current when medically used does not, as a rule, produce any external injuries. Such might be caused by a spark from a static machine, but it would be due to gross carelessness, and is very unusual. Burns, however, from the use of the galvanic current are not very uncommon. They usually occur under the electrode after it has been for a few moments stationary in contact with the skin. They occur in certain patients with extraordinary readiness, especially in those with organic spinal lesions, and where the sensation is somewhat diminished, and where also some trophic lesion might be supposed to exist. They are not confined, however, to this class of cases, but may occur in any one if the electrode be retained too long in any one place, and especially if it be allowed to become dry. These burns are peculiar in appearance and can usually be recognized at once. They are circular, as if punched out, about the size of a common pencil or a little smaller, comparatively deep, gray with perhaps a dark ring at the circumference, and frequently surrounded by a reddened area. The edges are sharp. Their peculiarity consists (1) in their painlessness and (2) in their size, regular form, their depth in comparison to their extent, and the sharp limitation of the area of tissue destroyed. One or more may occur under a broad electrode, and they are probably produced at those points where the contact is imperfect or the conduction in some other way impeded. They heal without much difficulty and leave no serious results.

Other unpleasant symptoms produced by currents in medical use may be mentioned for the sake of completeness, and also as an introduction to the more serious symptoms caused by stronger currents. Dizziness, vertigo, tinnitus, nausea, vomiting, and syncope are readily caused by even slight currents. The sensation of light in the eyes and the metallic taste in the mouth are the results of medical currents of ordinary strength when applied to the head or in its neighborhood, and stronger currents applied at greater distances cause these sensations. All the above symptoms may be readily caused by even slight currents, whether galvanic or faradic, passed through the head. The syncope thus produced is to be carefully differentiated from the syncope caused psychically by excitement or fear of the application of electricity. Hysterical women, and even persons who show no special signs of nervous instability, may faint at the suggestion of the application of electricity. I have seen a large, strong, well-built Italian man, perfectly sound physically, so far as could be detected, except some slight local neuralgia, faint from pure fright when the electricity was to be applied. But even the application of moderately severe shocks from the ordinary medical battery are not likely to produce serious results. These shocks are ordinarily caused by the opening or closing of the galvanic current, and are most severe when the current passes through some portion of the head. A still more powerful shock may be given by reversing the current in a galvanic battery by means of the commutator.

Currents of High Tension—Strong Artificial Currents.

Passing on now to the consideration of the stronger currents, we come to those used for mechanical purposes, for electric lighting, electric railways, and other analogous objects. These currents start from dynamos or from storage batteries, and accidents are caused by them whenever they are diverted from their proper course and are caused to come in contact with or to pass through any portion of the human body in any considerable strength. Accidents not infrequently occur from direct contact with the batteries or dynamos, but still more frequently they are produced in their circuit along the wires or transmitters. They may also be caused, as some of the most fatal have been, by contact with metallic or other readily conducting objects which have themselves accidentally come in contact with some portion of an electric circuit (usually wires) and have diverted the whole, or more usually a portion, of the current to themselves. Thus was killed a young man in New York, the clerk in a store, who while lifting the metal-edged cover of a show-case brought it in contact with the charged wires of an electric light and received an immediately fatal shock. As a rule, those meeting with accidents from dynamos or electric machines directly are employees of electric companies, who are presumed to have more or less knowledge of the risk of carelessness, or they may be workers in institutions or factories in which such machines are in use. Many of the accidents due to wires also occur to linemen and other employees of electric, telephone, or telegraph companies or of electric railway companies in charge of wires or electric outfit. So long as the current transmitters and terminals (wires, etc.) are properly insulated and in their proper position in relation to other conductors, it is unusual for accidents to occur, except in cases of gross ignorance or carelessness. Unfortunately, however, proper insulation is not always accomplished, and frequently wires and other transmitters are removed from their proper positions by accidents and otherwise. So long as and wherever the system of overhead wires exists, if there be among these wires any which are the transmitters of strong electric currents, there is always a risk, and often a very serious one, that at some time or other one of these current-bearing wires will come into contact with some other non-current-bearing and ordinarily harmless wire in such a manner that the current of the first should be diverted, in whole or in part, on to the ordinarily innocuous wire, which thereby becomes at once charged and dangerous. Such an accident may be due to the displacement of either wire or to any other cause which brings the two in contact, either direct or indirect, at a point where the current-bearing wire is not sufficiently insulated. The current having once passed out of its proper circuit will, of course, follow the paths of best conduction, and may hence suddenly appear in unexpected quarters and produce the most dangerous and even fatal effects. It is accidents of this character which most frequently occur among the people who are neither employees of electric companies nor engaged in factories or buildings where electrical machines are employed.

Insulation of Wires and Other Electrical Transmitters.—We cannot mention here the various methods employed to insulate wires, as the general principles of insulation are well known. Electric wires even with very strong currents can be insulated and can be kept insulated if sufficient pains be taken and sufficient money be expended. But this is very expensive and in many cases is not done. Only partial insulation is attempted, and even this is not always carried to the degree intended or stipulated. Hence so long as overhead wires of various kinds exist, accidents from the transmission of strong electric currents along ordinarily harmless wires are liable at any time to occur, as practically little or no attempt at keeping the current-bearing wires covered with a thoroughly insulating material is in most cases made. It is usually deemed sufficient that glass or other insulators should be so placed that under ordinary conditions the wire will not come into contact with any conductor which may cause any essential part of its current to diverge. In most cases a so-called insulating material is placed over the wire itself, but this usually is insufficient at the outset or becomes so before very long and is then not renewed.

It must not be supposed, however, that underground electric wires or transmitters cannot produce accidents. On the contrary, the current may be diverted from them to the gas or water pipes or to any other conductors which come into contact with them or can attract to themselves a portion of their current. Severe shocks have been experienced by persons attempting to draw water at their faucet from causes of this character. At the same time, so far as mere safety is concerned and freedom from electrical accidents, it would seem that underground wires are preferable to overhead wires.

Electrical wires have not infrequently come in contact with telegraph and telephone wires causing unpleasant results. Telephone boxes have been set on fire, and also telegraph boards and tables, and in certain cases what might have been serious conflagrations have been started in this manner. By means of proper arrangements on the telegraph and telephone circuits these dangers can be at least partially avoided, but there is always the risk that the automatic alarms and other contrivances do not act, and the still greater one that persons or things may come into contact with these charged wires and receive dangerous or serious injuries.

Electric Cars.—The danger from the overhead wires in the trolley system of electric cars would not be great were these wires properly supported, properly insulated, and properly protected. Each of these terms must be explained. Wires which fall for any cause whatever short of being intentionally removed cannot be deemed properly supported in the sense in which we use the term. Any one of these electric wires which falls is liable to produce serious injury to persons or animals (many horses have been killed by them), or to set fire to objects with which it comes into immediate or indirect contact, the amount of injury being in part dependent upon the nature and the condition (wet or dry) of the object and its position in relation to other conductors. Wires as dangerous as these car wires should be so supported that no ordinary accident, no condition of the weather, strong winds, or heavy falls of snow should be capable of wrenching them from their supports, and they should be placed in such positions and with such protection as not to receive blows from passing or falling objects.

Secondly, these wires should be properly insulated. This is to be understood to mean that all the wires which carry the electric current, or are liable to carry it, should be attached to their poles or other support in such a manner that no appreciable quantity of electricity is under any circumstances liable to be diverted to the poles or supports, and in this way cause destruction or injury. In addition to this the side wires should be so covered that if any accident occurs, it will be difficult or impossible for the current to pass away from them to other objects. The middle wire on which the trolley runs cannot be thus covered, but must be left bare, and hence, if knocked down or brought into contact with properly conducting objects, must be the most dangerous; but on the other hand from its position it is less liable to accidents.

When we say that these wires should be properly protected we mean that such arrangements and contrivances should be used as will prevent them while in their usual position from coming into contact with dangerous objects, particularly with other wires. This may be accomplished by guard wires or in other ways. It is plainly of great importance that this should be specially cared for, and particularly in a city where there are many overhead wires, and perhaps a considerable number of dead or non-used wires. If the electricity comes into contact with one of these no one can tell where it may be transmitted or what harm it may do.

The principles which apply to these overhead wires of course apply ceteris paribus to all other electric overhead wires, and in like manner the statements made in regard to the diffusion or spreading of currents in underground wires are applicable to all methods of transmitting electricity mechanically through the ground so far as the conditions are similar. An electric current will always follow the path of best conduction, and where several paths are opened it will follow them proportionally according to the excellence of their conduction or inversely to the amount of their electric resistance.

We shall not enter here into any questions in regard to the diffusion of electricity, its transmission through fluids, water, air or other gases, nor shall we discuss the relations of good or bad conductors to electricity except so far as this relates to certain portions of the human body. An elementary knowledge of physics and electricity must be presupposed.

We can now enter more directly upon the immediate subject of this article, that is, the effect upon the human body of severe or moderately strong currents of electricity derived from artificial sources. The accidents produced by these currents may be divided into two classes, the direct and the indirect. Under the direct we place all those conditions which are apparently produced by the action of the electricity itself, such as the general shock, the loss of consciousness, the burns, etc. On the other hand, all those accidents are to be considered indirect which are not primarily due to the action of the electric current, but are only secondary results thereof. These are largely determined by the immediate surroundings and conditions at the time. Such, for example, are the surgical injuries due to falls caused by the loss of consciousness produced by the electric shock.

Indirect Accidents.

These will be considered first, as they do not demand so detailed a description as the direct. They are traumatic in character and are the result either of loss of consciousness, momentary or lasting, or of the involuntary muscular contraction which may be occasioned by the electric shock. They are among the most frequent effects of severe electric shocks. These accidents consist in contusions, fractures, dislocations, wounds, and any other injuries which may be produced from sudden loss of consciousness while in a dangerous position. Death may readily occur either immediately or as the more or less delayed result of such injuries. If the person shocked falls into the water he may be drowned, or if into the fire he will be burnt. The varieties of such accidents dependent on the sudden loss of consciousness produced by the electricity are, of course, innumerable, and their occurrence must largely depend upon the position of the victim at the moment of the shock. We see, perhaps, most of these accidents in linemen on the tops of poles or houses or in other exposed places, but persons who receive shocks when simply standing on the ground or when sitting are not exempt from severe surgical injuries other than burns. They are often cast to the ground with great violence, and not infrequently are thrown to a distance of several feet. This is caused by the violent muscular contraction produced by the electric shock, and it may occasion, like any violent push or fall, severe injuries from contact with the various objects against which they may be forced. Although much rarer, it is also possible that the violence of these muscular contractions may be such as of themselves to cause injury, as rupture of a muscle or tendon. As practically all these indirect accidents are traumatic and surgical in character, they do not differ from other accidents similar in kind, but otherwise caused, and are to be treated on the same general principles as these.

Direct Accidents.

Quite different from the indirect are the direct accidents; those produced by the immediate (direct) action of the electricity. These are of various kinds, which we shall consider separately. They may be divided into immediate and late symptoms, and they vary much according to the severity of the shock and the constitution of the patient, and the part of the body through which the electricity passes. The character of the current which gives the shock, whether constant or interrupted, also naturally has an influence on the effect.

General Principles.—A shock may be given in three ways with an ordinary galvanic battery. If the current be sufficiently strong, a distinct shock will be produced when the circuit is closed and again when the circuit is opened, while with a current of the usual strength for medical purposes, the sensation while the current is passing through the body steadily is much less and is often limited to a sensation of burning at the seat of the electrode. A shock may also (thirdly) be produced by a reversal of the current, and the shock thus caused is stronger for the same current than that produced in either of the other ways.

The strength of these shocks is shown both by the sensation produced and by the amount of muscular contraction caused. When now a shock is caused by a continuous or constant current which starts from an ordinary dynamo or other electric generator or storer, it is practically always caused by the opening or closing of the circuit, or, what is essentially the same, the diversion of a part or the whole of the current from its proper path to and through some portion of the human body causes a shock at the time of the entrance of the body into the circuit and another at the time of its exit therefrom. Shocks from reversal of current when such current arises from a constant machine might occur, but only through some peculiar accident. Hence the shocks (distinguished from any other effects of electricity) which are received by the person coming into contact with a constant current are felt only at the moment of entering the circuit (closure) and of leaving it (opening). If a person introduces himself between the two wires of an electric circuit in which a constant current is used, in such a manner as to cause the current to pass through his body, he will feel the shock only at the moment when he touches the second wire and completes the circuit, and at the moment when he lets go one of the wires and opens the circuit (unless the current be so strong or be so placed that he can divert to himself sufficient electricity to cause a shock, or, in other words, close a secondary circuit in some other way). While the current is passing through the body, although it may burn and cause tingling and other unpleasant symptoms, there is no proper shock. In other words, an electric shock is caused only by a change in the amount of electricity passing through the body or a portion thereof.

If we now consider the effects of alternating currents, we find that we have another factor to deal with. The general principles are exactly the same, but inasmuch as the reversal shock is stronger than the closure or opening shocks, other things being equal, we are likely to receive a stronger shock from a current of the same force, and in addition to this, as in alternating machines the reversals occur with considerable rapidity, the person who becomes connected with this circuit receives a number of strong shocks within a short space of time. This is a much more serious matter than to permit a current of equal strength to flow through the body without change.

—The effect of this form of electricity on the human body is first stimulating and then tetanizing to the muscles. It consists in a very rapidly interrupted current, the shocks being at times so frequent that they are not singly perceptible. There is probably also a distinct difference in the action of this current from that of the galvanic current aside from its rapid interruption. This is not, however, of so defined a character as to enable us at the present time to distinguish in man the results of severe injuries and deaths caused by this form from those caused by other strong currents. Practically this form of current is but little used, except in medical batteries and for the purposes of experimentation in laboratories.

Static electricity has, so far as we know, rarely or never caused serious injuries or death. The sparks produced in this way have sometimes caused burns, and it is conceivable that a strong electric current produced in this way might be dangerous. The symptoms could not be distinguished from those caused by other forms of electricity.

Summary.—The greatest source of danger from electric currents is the shock produced by them. In ordinary constant or continuous currents this is produced only at the moment of the opening and the closure of the circuit. In alternating currents a shock is also produced at each reversal of the machine. Faradic and static currents are rarely or never used mechanically or in the arts.

Resistance.—The resistance of the human body to electric currents has been very variously estimated.

The reasons for these variations are: (1) that the different tissues present different resistances; (2) that the resistance in the same tissue varies greatly under different circumstances.

The tissue which offers the greatest resistance and also practically the greatest variation is the skin, or, more properly speaking, the epidermis. The resistance of this is many times as great as that of the rest of the body, and when perfectly dry it is impervious to currents of great strength. Witz states that in using a Ruhmkorf coil with an estimated force of 250,000 volts in Guinea-pigs and rabbits, it is advisable to cut through the skin in order to apply the electrodes directly to the flesh, or, at least, to wet the skin thoroughly, otherwise the shock caused by the full strength of the battery (six jars charged from the coil) would not cause death. Various animals offer rates of resistance which vary somewhat apparently according to the nature of the animal, but are probably largely dependent on the conducting power of its tissues, that is, of its skin. The variations between the resistance of similar animals, according to the condition of the skin at the time of the experiment, are much greater than those which are found between animals of different species under similar conditions, or which are referable to specific susceptibility. Mr. Harold P. Brown testified in the Kemmler case (Court of Appeals, State of New York—State of New York ex rel. William Kemmler against Charles F. Durston, agent and warden) that he had in the course of his experiments seen a horse weighing 1,320 pounds, with a resistance of 11,000 ohms, killed by an alternating current at 700 volts.

The resistance of the different cutaneous surfaces of the human body as measured by Jolly in Siemens’ units was from 400,000 down to 15,000 in the male and to 8,000 in the female (Siemens’ unit is to the ohm as 1.06 to 1.00).

Tschirfew and Watteville made the resistance from 80,000 to 3,000 ohms.

Experiments made at the Edison Phonograph Factory and Edison Laboratory in July, 1889, on 259 males between the ages of eleven and fifty-one, showed a resistance, measured between the hands immersed to the wrists in a solution of caustic potash independent of polarization, averaging 986 ohms and varying from 1,970 to 550 ohms.

The resistance of 236 men employed at Messrs. Bergmann & Co.’s Electrical Works in New York appears to have averaged 1,184 ohms and to have varied from 1,870 to 610 ohms. These measurements were also taken between the hands, which were washed with soap and water and then dipped in jars containing a solution of caustic potash. The battery consisted of four chromic-acid cells each having an E. M. F. of 2 volts.

As shown in all the experiments on animals and more especially in the cases of electrocution, the continuance or duration of the current has much effect on the resistance. As the current continues the resistance diminishes. Thus in the case of McElvaine the resistance between the immersed hands was at the beginning 800 ohms and at the end of the contact of fifty seconds had decreased to 516 ohms. In this case, when the current of 1,500 volts was applied from the forehead to the leg, the resistance was practically steady at only 214 ohms. Of course the small resistance in these cases (electrocutions) depends largely on the perfect contact secured.

According to the amount of resistance offered do the effects of severe shocks of electricity differ. This is shown especially well in the action of lightning, but is also true of powerful currents produced mechanically. If the resistance of the skin be slight at the moment of entering the circuit of a strong current, the current will pass through it with comparative ease and without causing much injury; but if on the other hand the resistance is great, the current will be, as it were, momentarily retarded or stored, heat will be developed, and there will ensue a burning and charring of the tissue of a special kind. These burns occur principally at the places where the current is specially resisted, that is, at the point of entrance of the current to the body and at its point of exit. This is the cause of the frequent burns in the heel or sole of the foot in the case of those struck by lightning while standing, as the electricity passes away from the body into the ground and finds a strong resistance at the point of leaving the body. This is also the cause of the burns where the current leaves the body from any other cause, as from the contact or proximity of a metallic object. The greater the resistance so long as the current passes, other things being equal, the more severe is the burn. It is for this reason that in medical electricity we usually use wet sponges on the skin or electrodes moistened with salt and water or with other fluids which will assist in rendering the passage of the electricity through the skin more easy. Solutions of chlorid of sodium and of certain other salts do this.

The mechanical effects of currents vary thus according to the resistance encountered. They also vary according to the intensity or concentration of the current. If a current of moderate force be applied through a small metallic point, it will burn, pain, and produce active irritative symptoms, while if the same amount be applied over a large surface simultaneously, it may have little or no irritating effect. We have, therefore, three factors in determining the mechanical effect of any electric current on the body: (1) the condition of the body, that is, the amount of resistance which the current will encounter at its entrance and exit; (2) the amount and intensity of the current; and (3) the character of the current. For practical purposes of the more severe currents we have only to deal with the continuous and alternating.