US3834374A

US3834374A - Diagnostic electrical scanning

Info

Publication number: US3834374A
Application number: US00241635A
Authority: US
Inventors: M Ensanian
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-04-06
Filing date: 1972-04-06
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: BE819659A

Abstract

Body surface bioelectrical potentials are determined and recorded by use of a stationary electrode in contact with the body surface and an exploratory electrode which comprises a rotatable element, that preferably carries an electrolyte. Scanning of the body surface along a continuous path or over an area is carried out by rolling at least one exploratory electrode over the said surface, thus permitting mapping of the potentials along the line or over the area contacted by the exploratory electrode, whereby abnormalities of the skin or portions of the body under the skin may be detected.

Description

United States Patent [191 [111 3,834,374 Ensanian 5] Sept. 10, 1974 [54] DIAGNOSTIC ELECTRICAL SCANNING 3,323,515 6/1967 Foner et a1 128/2.06 R [76] Inventor: Minas Ensanian, PO. Box 98, I

Eldred, p 1 731 PrtmaryExammer-Wrlham E. Kamm Attorney, Agent, or Firm-Ashlan F. Harlan, Jr. [22] Filed: Apr. 6, 1972 [21] Appl. No.: 241,635 Body surface bioelectrical potentials are determined [52] 128/ 128/ and recorded by use of a stationary electrode in 51 I Cl A64, contact with the body surface and an exploratory elec- 'f i G 2 06 R trode which comprises a rotatable element, that pref- 1 g 2 2 1 4 erably carries an electrolyte. Scanning of the body surh 4 face along a continuous path or over an area is carried out by rolling at least one exploratory electrode over the said surface, thus permitting mapping of the po- [56] References cued tentials along the line or over the area contacted by UNITED STATES PATENTS the exploratory electrode, whereby abnormalities of 1,049,759 l/1913 Oliver 128/405 the skin or portions of the body under the skin may be 1,681,628 8/1928 Schwarzkopf et al. l28/2.06 G detected. 2,546,275 3/1951 Redding l28/2.l R 2,736,313 2/1956 Mathison 128/2.1 Z 7 Claims, 20 Drawing Figures NIED SEN 01914 H If 5 PAIENTEBsmomn 3' 4374 v flllllllllllll lllll "I" PATENTEBSW'B m w 6 3.834.374

DIAGNOSTIC ELECTRICAL SCANNING BACKGROUND OF THE INVENTION This invention relates to a process for dynamically measuring and recording bioelectrical potentials on the body surface and to mapping the body surface or portions thereof with respect to such potentials.

Electrical measurements are commonly employed in diagnosis of heart and brain conditions and disorders. Electrocardiograms are routinely used to detect cardiac lesions and other cardiac abnormalities. Electroencephalograms which reflect the activity of the brain are widely used in the examination of patients having brain tumors and lesions. In both cases electrical currents generated in the respective organs are recorded and the recorded wave patterns are interpreted by comparison with other recordings. The recording is accomplished by determining the generated potentials between a plurality of electrodes applied to the body surface at predetermined points or betweentwo or more electrodes at least one of which is successively applied to different points on the body surface.

SUMMARY OF THE INVENTION It has been discovered that with apparatus that is much less complicated than that previously used in obtaining electrocardiograms and electroencephalograms bioelectrical potential readings can be obtained by scanning along a line or over an area of the body surface. Such readings in many cases provide meaningful data as to the condition of the skin and underlying organs or other portions and may permit diagnosis of body conditions. The potential readings can be taken continuously along a path on the body surface using only two electrodes. Apparatus suitable for determining the body surface potential according to the invention is disclosed in copending U.S. patent application Ser. No. 79,033, filed Oct. 8, 1970.

The present process consists in feeding the continuous electrical potential reading obtained between two electrodes to a suitable recording instrument such as a strip chart recorder. One of the electrodes is stationary and in contact with the body at a suitable location. The second or exploratory electrode comprises a rotatable element which is rolled over a predetermined path on the body surface, the variations in potential along the path of the electrode being shown as a continuous line or trace on the recorder chart. Obviously, when the exploratory electrode is moved with substantially constant speed there is a virtual one to one correspondence between points along the recorded trace and points on the skin along the path of the electrode that can be readily used to determine the potential at any such point on the skin. Changes in the potential along the path of the exploratory electrode are indicative, not only of changing skin resistance but also of the electrical activity of organs and other bodyportions beneath the skin. Preferably the rotatable element of the-exploratory electrode carries an electrolyte to ensure good skin contact. It will be understood, however, that the velocity of the rolling electrode does not affect thepotentials measured. Potential mapping of an area of body surface can be accomplished by successive use of the same exploratory electrode along different, closely adjacentportions thereof or by using a plurality of exploratory electrodes simultaneously.

SHORT DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially schematic view of apparatus suitable for carrying out the present invention;

FIG. 2 is an enlarged, detail view of a portion of the exploratory electrode shown in FIG. 1;

FIG. 3 is a sectional view on line 33 of FIG. 2;

FIG. 4 is a simulation of typical oscillatory scanning patterns;

FIGS. 5 to 19, inclusive, are drawings showing the essential features of the scanning patterns or traces recorded in carrying out scannings on various portions of a body surface as described hereinafter; and

FIG. 20 is a partially schematic view of a modified form of apparatus.

DESCRIPTION OF THE INVENTION As pointed out above, the present invention provides a diagnostic method which by scanning the electrical potential of the body surface, i.e. continuously determining such potential along a path on the skin, establishes the location of certain conditions or abnormalities on or under the skin. In the following examples a number of possible uses for the method are set forth.

Apparatus suitable for carrying out the method of the present invention is disclosed in copending U.S. patent application Ser. No. 79,033, filed Oct. 8, 1970. In FIGS. l-3 of the drawings of the present application there is illustrated an embodiment of such apparatus which comprises a pair of electrodes, one of which has a rotatable element that carries an electrolyte to insure good electrical contact with the skin and the other of which is adapted to be held in stationary contact with the skin, a strip chart recorder, and an electrical conductor between each of the electrodes and the input terminals of the recorder. In the illustration in FIG. 1, a scanning is being taken on the forearm of a subject.

More specifically, in FIG. 1 there is shown a recorder 21 having

input terminals

23 and 25. Attached to the terminal 23 by a suitable electrical conductor such as a wire or cable 27 is an electrode 29 which is preferably formed of metal and may have any desired shape or structure to permit it to be held in contact with the body surface. To the other input terminal 25 there is attached by a suitable electrical conductor such as a cable or wire 31 an exploratory electrode comprehensively designated 33, details of which are shown more clearly in FIGS. 2 and 3. Preferably, the conductive wires or cables are provided with electrical shielding. The electrode 33 comprises a stem or shank portion 35, to which the wire 31 is preferably attached and an axle portion 37 which extends laterally from the shank portion. The outer part of the axle portionis reduced in diameter, thus forming a shoulder 39. The electrode 33 also has a rotatable element which comprises a wheel having a hub 41, preferably fonned of metal, on which there is suitably secured a conductive tire 43 formedof a gelled electrolyte solution. The wheel is rotatably mounted on the reduced portion of the axle 37 between the shoulder 39 and a removable retaining member such as a ring 45 that is snapped into a groove adjacent the outer end of the axle 37. An electrically insulating handle 47 is provided on theshank portion 35 of the exploratory electrode 33. The'numeral 49 designates a strip chart produced by the recorder and bears a line representing electrical potentials on the surface of the arm along the path followed by the rotatable element of the electrode 33. As depicted in FIG. 1, the exploratory electrode 33 is being rolled along the forearm 51 of a subject and the stationary electrode 29 is clipped to said forearm.

It will be understood that the rotatable element of the electrode 33 can take other forms and be mounted in other ways. Thus, forv example, there may be used, instead of the electrode shown, one constructed as shown and described in the above-mentioned copending application, in particular, the structures illustrated in FIGS. 9, and 13 of the drawing of said application. The said figures and the descriptions thereof are hereby incorporated herein by reference.

Those skilled in the art will understand that strip chart recorders, such as are preferably employed in carrying out the-present invention, are capable of adjustment in ,a variety of ways. Not only can the chart speed be changed, but also the sensitivity and, for 'example by reversing the leads to the electrodes, the polarity. The chart ordinarily has a center line indicating zero potential (denoting at 0 in FIG. 1) and the recording pen draws on one side or the other thereof, depending upon polarity, at a distance from the zero potential line proportional to the received voltage. Since, how'- ever, the sensitivity can be adjusted, the actual distance from the zero potential line of a point on the recorded line or trace responsive to a specific voltage will be greater or less depending upon the sensitivity range chosen for the recording.

' It will also be understood that the amplitude and frequency of the electrical impulses and currents occurring in the body which result in different skin potentials vary and that the skin is known to act as an antenna, picking up electrical radiation. Consequently, the width of the trace drawn by the oscillating pen of the recorder will vary. In FIG. 4 there are shown four sections of astrip chart 53 which illustrate the effect on the trace width of skin resistance. Progressing from section a of the chart to section d thereof, the skin is shown to'have decreasing resistance. In section a the skin re- 'sistance isquite high, while in section d it is quite low.

A relatively wide trace on the chart will also be obtained when one or both of the electrodes is not in contact with the body surface since in such case stray alternating current fields are picked up and recorded. The actual width of traces drawn on the recorder will be determined both by the voltage and the sensitivity thereof. It should be remembered that where the trace is relatively wide, the potential indicated is that of a point midway between the parameters of the trace. In many instances, the chart speed is too slow to show the trace as oscillations so that the trace on the chart appears as a solidly inked area without visible oscillations. In the reproductions of the recorder chart portions hereinafter referred to, the wider traces are for convenience arbitrarily shown with horiiontal lines that represent such oscillations. I

In carrying out diagnostic procedures by the present method, the location and type of the stationary electrode is not usually important. It may be held in the tingers of the subject, may be clipped to the body, or may be held or clampedto the body with or without a suitable electrode paste to improve electrical contact with the body surface.

EXAMPLE 1 For this example a plurality of tests were made which demonstrate that non-visible alteration of the skin surface cen be detected and recorded by the novel method of the invention.

In each test a small amount of a corrosive liquid was placed on the skin of the forearm of a'subject, the arm being immobilized and resting against a background chart having ruled lines thereon which permitted-the location of the liquid. application to be established. The liquid was removed from the skin by thorough wiping and theskin was then allowed to dry. After drying, no evidence of the treatment was visible to the eye. Then, using apparatus substantially like that illustrated in FIG. 1, the wheel of the exploratory electrode was run over the arm from wrist to elbow while the stationary electrode was firmly grasped in the other hand. It was observed in each test that, as the exploratory electrode passed over the area on which the corrosive liquid had been placed, there was a sudden marked increase in the recorded potential which decreased again to the normal voltage after the rolling electrode had passed over the treated area.

Tests were made with dilute NI-I OI-I solution and dilute HNO solution. In each case the trace on the recorder chart located the treated area on the arm of the subject as determined by comparison with the rulings on the background chart. FIG. 5 is a reproduction of an area A on the recorder chart showing the deviation from normal potential over the treated skin area when dilute nitric acid was used.

It will be evident from the foregoing that victims of accidents involving the spilling or spraying of corrosive materials may be easily treated for latent burns or skin damage by using the present novel method to locate the affected and potentially damaged areas of the skin.

One of the simplest determinations or diagnoses that may be made by the present novel method is a determination as to whether muscles are relaxed or in tension. This is illustrated in the following example.

EXAMPLE 2 Using apparatus substantially like that illustrated in FIG. 1, tests were made on an arm of a subject. The stationary electrode was in contact with the hand of the subject. The exploratory electrode was run longitudinally of the arm of the subject from the wrist area to the biceps area while the arm was relaxed and resting on a table. The trace on the recorder chart showed that the potential throughout the length of the path on the arm was almost constant, there being a potential difference along the path of only about 50 mv. When, however, the arm muscles were tensed by the subject, a reading taken while rolling the exploratory electrode along the same path on the arm showed a difference in potential of about mv from the wrist to the biceps. FIGS. 6 and 7 are reproductions of the portions of the recorder chart showing the varying potentials with the arm muscles of the subject relaxed and tensed, respectively.

The following is another example of the location of a latent injury to the body by use of the method of this invention.

EXAMPLE 3 In this test, using the same general technique as that described in the preceding examples, a recorded potential line or trace was obtained with the rolling exploratory electrode from the forearm of a subject while the arm was resting on a table. Then, without warning to the subject, a hot heat lamp was brought into momentary contact with the forearm. Another potential line was immediately recorded by rolling the exploratory electrode over the same path on the arm. Substantial reproductions of the potential lines or traces obtained before and after the burn are shown, respectively, in FIGS. 8 and 9. At the time of making the second recording, there was no visible evidence of the burn on the arm. Subsequently, a severe burn became evident in an area of the subjects arm corresponding to the region B of the trace shown in FIG. 9.

As will be seen in comparing FIGS. 8 and 9, the normal trace varied little in potential, only about 100 mv, while the trace obtained after application of the heat lamp was irregular, varying several hundred mv in potential, and showed extensive oscillation over a considerable region on each side of the region B.

Still another example of the location of latent injury to the body is set forth in the following example.

EXAMPLE 4 Using substantially the same technique as that described in Examples 2 and 3, a normal potential line or trace was obtained on the recorder by running the exploratory electrode along the relaxed forearm of a subject. A substantial reproduction of this trace is shown in FIG. 10. It indicates a change in skin potential of only about 60 mv from the wrist to the inner elbow. A sharp, hard blow with a wooden rod was then given on the arm. Another trace over the same skin path was recorded after the blow was inflicted. The second trace showed a potential variation of over 400 mv and considerable oscillation. This second reading is substantially reproduced in FIG. 11. Although a bruise subsequently was observable on the subjects arm at a point thereon corresponding to the region designated C in FIG. 11, potential changes over the area struck were clearly evident before the bruise could be seen.

As shown in the following example, the method of the present invention may also be used in studying and locating abnormalities in the circulatory system of the body.

EXAMPLE 5 In this example there is set forth a test for detecting restricted circulation in the arm of a subject. For test purposes such restricted circulation was produced by a tourniquet applied to the upper arm of the subject.

Substantially the same procedure as that described in Example I was used. FIG. 12 is a substantial reproduction of the trace or potential line recorded, when the exploratory electrode was run from the wrist to the upper arm of the subject, with the arm relaxed. FIG. 13 is a substantial reproduction of the line or trace obtained along the same path immediately after a soft rubber tube as a tourniquet was applied to the upper arm and tightened. FIG. 14 is a reproduction of the trace obtained along substantially the same path after the tightened tourniquet has been in place forapproximately one minute. Application of the tourniquet to the arm with the resultant reduced blood circulation is clearly evident in the recorded traces, the relaxed arm trace showing a substantially constant potential and a rapid change (see FIG. 13) occurring when the tourniquct is tightened. Even after a quite short interval of re-' duced circulation, the recorded trace (FIG. 14) is very irregular, showing much oscillation.

The following example sets forth still another use of the method of the invention in locating the site of an injury to the body.

EXAMPLE 6 FIGS. 18 and 19 substantially reproduce the traces obtained by the present novel method-before and after, respectively, making a small puncture in the forearm of a subject. The left arm of the subject was rested on a table and, with the arm relaxed, a recording was made by rolling the exploratory electrode from the wrist region to the inner elbow region. The stationary electrode was held in contact with the left hand of the subject. A fine puncture was then made in the skin of the forearm and another recording was immediately made by passage of the exploratory electrode over substantially the same path as before. Although the puncuture was not visible to the eye, the second recording indicated its location by the deflection in the trace indicated at D in FIG. 19. It will be noted that in FIG. 18 the potential along the line of travel of the exploratory electrode is rather constant, varying only about 65 mv while in FIG. 19, after the puncture was inflicted, the trace is of greater amplitude and the potential varies as much as about 300 mv.

It will be evident from the foregoing example that the present method may be put to practical application in locating slivers of metal or nonconductive materials, e.g. glass, in the skin even when the skin surface shows no visible sign of the point of entry thereof.

From the foregoing examples, it will be obvious that the scope of use of the present novel process is quite wide. Other possible diagnostic uses of the process will be discussed below. It is not to be understood, however, that all such possible uses are discussed or even mentioned, since the field of potential or desirable use is extremely broad inasmuch as the present method may be used on any part of the body.

As pointed out earlier herein, electrocardiograms are important in determining the condition of the heart and diagnosing abnormalities thereof. It is known that the heart is not usually oriented in a perfectly vertical position in the body. Consequently, the electrical axis or zero potential plane of the hearts electrical field is not the same in all persons. Moreover, such axis is known to be subject to change as a result of damage to the myocardium and for other reasons. It is, therefore, often important to determine the electrical axis. This can be easily and very quickly done by the process of the presv ent invention.

In the normal, known method of determining the electrical axis of the heart, six electrodes disposed at different points on the chest are required. The varying potentials detected by these electrodes are recorded by a plurality of pens on a strip chart recorder and the recorded data is interpreted and analyzed. By the method of the present invention, however, to determine such axis it is only necessary to run the exploratory electrode across the chest of a subject in two or more spaced, parallel paths. When the electrical axis is crossed there is a reversal of the direction of the spikes which represent the pulses of the heart beat on the recorded lines or traces. This reversal of polarity indicates a transition by the electrode from the positive half of the hearts electrical field to the negative half thereof. Consequently, the electrical axis can be determined by connecting the points on the chest of the subject which correspond to the points on the recorded traces where the polarity reversal of the heart beats take place. The resultant line is the electrical axis.

FIGS. 15 and 16 are substantial reproductions of portions of a recorder chart showing traces typical of those produced by the present process, the letter E indicating the pulses of the heart beat and the letter F indicating the region corresponding to chest areas proximate to the zero potential plane of the heart. In making the recordings from which FIGS. 15 and 16 were drawn, the stationary electrode was connected to the left ankle of the subject. Obviously the hearts location can be determined by comparing the traces obtained by running the exploratory electrode along a plurality of body paths in the proximity thereof including, if desired, paths on the back and sides of the subject.

It will be evident that the use of an exploratory electrode in accordance with the present method for determining the location and orientation of the heart is faster and easier than the conventional procedure. In many cases this is highly important since delays in obtaining information about the heart often are factors contributing to the death of a patient.

Another use for the method of this application is the determination and recording of the electrical activity of the brain. As in the conventional way of producing electrocardiograms, electroencephalograms are conventionally obtained by the use of a number of electrodes. These are applied at various locations on the shaven head of a subject. It has been found that by attaching a stationary electrode to one ear of a subject and running the exploratory electrode across the subjects forehead brain waves can be easily recorded on a strip chart recorder. Obviously, this procedure is less time consuming and simpler than shaving the subjects head and applying a-plurality of electrodes thereto. FIG. 17 is a substantial reproduction of a typical wave recording according to the present method. It will be obvious that scanning with a rolling electrode can also be carried out over any other desired portion of the head, indeed a potential mapping of the entire head surface can be readily obtained; and that from the re- 'sulting recorded traces abnormalities of the brain, such as tumors, can be located.

As indicated above, it may be desirable or necessary for study or diagnosis in some instances to determine the body surface potential along a plurality of related lines on such surface. This is illustrated in FIGS. 15 and 16 which show the traces obtained by a pair of parallel passages of an exploratory electrode made to locate the electrical axis of the heart. Where parallel paths are desired, a plurality of exploratory electrodes 33, according to the invention, may be, as shown in FIG. 20, mounted together in a unit 61, each electrode being connected by a suitable lead 31 to a separate input terminal and pen of a strip chart recorder so that two or more traces can be made at once. In other cases, it may be desired to have the paths followed by the exploratory electrodes intersect. For example, in FIG. 14 the potential reversal designated by the letter G, where the trace crosses the line of zero potential on the chart, indicates the crossing of the pulse or arterial pressure point in the wrist of the subject. When the exact location of this point is required, one ormore additional traces obtained by rolling the exploratory electrode over the same region will pinpoint the location. As previously pointed out, the potentials at many different points over specific body areas can be mapped by covering such areas with multiple scannings by one or more exploratory electrodes, either successively or simultaneously.

It will be understood that the traces showing body surface potentials obtained by carrying out the present method reflect not only the skin potential but also the electrical pulses of organs, nerves, muscles, and other body elements beneath the surface which are superimposed thereon. Indeed, if desired, the method can be employed to pick up and record electrical currents impressed on the body, for example, those used in electroanesthesia and electroanalgesia. Such currents will also be superimposed on the traces of skin potentials.

As pointed out above, the construction of the electrodes employed in carrying out the present process may vary within wide limits. The exploratory electrode, however, must have a rotating element that rolls over thebody surface and preferably such element carries an electrolyte solution to ensure good electrical contact with the skin. The size of the rotating elements can vary as desired although generally it is preferred for increased accuracy to have both the diameter and the width or thickness thereof relatively small. For example, a roller about 7 mm thick and having a diameter of about 25 mm has been found quite satisfactory.

The pressure employed on the exploratory electrode incarrying out the present method may also vary. Differences in pressure may cause quantitative changes in the recorded potential lines or traces, but not qualitative ones. However, it is desirable to use light pressures since this will minimize any skin or muscle reaction to passage of the electrode. In most cases a pressure-of about l0g/cm is satisfactory although less pressure can be used if desired. In recording body surface potentials that are to be compared or in potential mapping of a body surface,it is of course important to employ the same pressure on the exploratory electrode and preferably the same velocity of scanning in the several scannings made. It has been found that under substantially similar circumstances and external conditions the traces obtained on the strip chart are reproducible for the same subject and that similar types of traces are obtained when subjecting different subjects to the same stimuli or events- In carrying out the method of the present application, at least that portion of the exploratory electrode which contacts the body surface or is separated therefrom only by the electrolyte solution is preferably of silver although any other common metal can be used. When a gel of an electrolyte solution is employed, sodium chloride is preferred as the electrolyte since it is physiologically neutral, but other harmless salts can be used. A satisfactory gel can be produced by forming a solution of 0.5 g NaCl and 14 g of gelatine in sufficient water to form ml of solution. The solution is then allowed to set in molds of the desired shape and mounted on or used as the rotatable element of the electrode. It is generally desirable to have the electrolyte on the rolling element of the exploratory electrode in such form asto prevent or minimize the leaving of a deposit of electrolyte on the body surface during scanning in which electrical contact between the electrode and the body surface is made through the electrolyte.

It will be evident from the foregoing description that the method set forth in this application is of use in a wide variety of circumstances and has great value in determining and diagnosing body conditions. It will also be evident that there are many possible variations of the described procedure that can be used either to obtain information of the type herein described or other information as to body conditions and functioning.

I claim:

1. A process for recording bioelectrical potentials in a living body which comprises establishing electrical contact between the body surface and a first electrode through an electrolyte which forms a portion of a solid rotatable element, said element having a continuous circular periphery, establishing electrical contact between the body and a second electrode at a point on the 2. A process as set forth in claim 1 comprising repeatedly rolling said first electrode along said path and continuously recording the potential between said electrodes during each of the retracings of said path.

3. A process as set forth in claim 1 comprising rolling said first electrode along a plurality of closely adjacent paths on the body surface and continuously recording the potentials between said electrodes in the movement of said first electrode along each of said paths.

4. A process as set forth in claim 1 in which a plurality of said first electrodes is employed, each being electrically connected through a recording device with said second electrode, comprising continuously recording the potentials between each of said first electrodes and said second electrode along the paths on the body surface taken by said first electrodes.

5. A process as set forth in claim 1 in which said electrolyte is in gelled, self-sustaining form.

6. A process as set forth in claim 1 in which said electrolyte is NaCl.

7. A process as set forth in claim 1 in which said electrolyte is in gelled, self-sustaining form.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent'No. 3,834,314 Dated September 9 Inventor (s) Minas Ensanian It is certified that error appears 'in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In line 1 of claim 7 "1" has been changed to Signed and sealed this 17th day of December 1.974.

(SEAL) Attest:

McCOY M.' ,GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM Q uScomm-oc we ve-Peg U- s. GOVERNMENT PRINTING OFFICE '99 36-38

Claims

2. A process as set forth in claim 1 comprising repeatedly rolling said first electrode along said path and continuously recording the potential between said electrodes during each of the retracings of said path.
3. A process as set forth in claim 1 comprising rolling said first electrode along a plurality of closely adjacent paths on the body surface and continuously recording the potentials between said electrodes in the movement of said first electrode along each of said paths.
4. A process as set forth in claim 1 in which a plurality of said first electrodes is employed, each being electrically connected through a recording device with said second electrode, comprising continuously recording the potentials between each of said first electrodes and said second electrode along the paths on the body surface taken by said first electrodes.
5. A process as set forth in claim 1 in which said electrolyte is in gelled, self-sustaining form.
6. A process as set forth in claim 1 in which said electrolyte is NaCl.
7. A process as set forth in claim 1 in which said electrolyte is in gelled, self-sustaining form.