US2400583A - Method and apparatus for conduct - Google Patents

Description

May 21, 1946. M, 5. WHITE 2,400,583

METHOD AND APPARATUS FOR CONDUCTING ELECTROCARDIOGRAPHIC EXAMINATIONS Filed May 22, 1942 4 Sheets-Sheet 1 Fig v V ELEGTROOARDIOGRAPH 959' ELEGTROOARDIOGRAPH m s/won MAJOR 6. WHITE May 21, 1946. M. 5. WHITE 2,400,583

METHOD AND APPARATUS FOR CONDUCTING ELECTROGARDIOGRAPHIC EXAMINATIONS Filed May 22, 1942 4 Sheets-Sheet 2 Fig. 2.

mvE/vroR MAJ 0} 6. WHITE Ana'q au-oluu u-f ATTORNEYS May 21, 1946;. 3, WHITE 2,400,583

METHOD AND APPARATUS FOR CONDUCTING ELECTROCARDIOGRAPHIC EXAMINATIONS Filed May 22, 1942 4 Sheets-Sheet 3 INVENTOR R 8. WHITE ATTORNEYS Patented May 21, 1946 METHOD AND APPARATUS FOR CONDUCT- ING ELECTROCARDIOGRAPHIC EXALIINA- TIONS Major S. White, United States Army Application May 22, 1942, Serial No. 444,080

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates generally to electrocardiographs but more particularly to a method and means for controlling the path of current through electrodes contacting various parts of the body or bodies of one or more patients under examination to determine heart voltages with respect to different current paths.

One object of the invention is to provide a device, used in conjunction with an electrocardicgraph by which various current paths from the patient to the electrocardiograph may be selected without the necessity of changing the location of the electrodes on the body of the patient to thus facilitate speed and ease of examination.

Another object of the invention is to provide for use, with the electrocardiograph, of precordial electrodes in addition to the electrodes now commonly used, and to adapt the instrument for the instantaneous selection of current paths from any of the electrodes connected to one or more patients. I

With these and other objects in view, the invention consists in a novel method of cardiographic examination of patients, and novel details of construction, combination and arrangement of parts of the apparatus devised to effect the examination, as will be more fully hereinafter set forth and pointed out in the claims.

Referring to the figures in which like parts are indicated by similar reference characters:

Fig. 1 is a perspective exterior view of the housing enclosing the circuit control device for a single patient showing the selector dial and leads to an electrocardiograph;

Fig. 2 is a perspective view of the housing shown in Fig. l, with top removed, showing the interior thereof with circuit control mechanism.

and lead connectors;

Fig. 3 is a diagrammatic view of the circuit control mechanism shown in Figs. 1 and 2;

Fig. 4 is a horizontal section taken on the line 44 of Fig. 2, looking in the direction of the arrows;

Fig. 5 is a horizontal section taken on the line 5-5 of Fig. 2, looking in the direction of the arrows;

Fig. 6 is a vertical section taken on the line 6-5 of Fig. 4;

Fig. '7 is a detail vertical section taken on the line 1-4 of Fig. 4;

Fig. 8 is a perspective view of a modified form of the device showing the exterior of the housing enclosing the circuit control apparatus adapted to form circuits to an electrocardiograph through various pairs of electrodes connected to a group of patients;

Fig. 9 is a perspective view of the housing shown in Fig. 8 with the top removed showing the interior thereof with circuit control mechanism and lead connectors;

Fig. 10 is a diagrammatic view of the multiple patient circuit control mechanism.

Of the instruments described herein, that shown in Figs. 1 to 7 inclusive is adapted to be used with a single patient and was devised to obtain precordial leads by the various recom mended methods as well as the standard leads, so as to obviate the changing of lead wires or electrodes during the process.

The modified form of instrument shown in Figs. 8 to 10 inclusive was designed so that, by operating a switch, it would be possible to connect several patients in succession to a single electrocardiograph machine at a rapid rate, as may be required in certain investigations, or in the examination of large groups.

Referring to the single patient instrument, the wiring diagram Fig. 3 shows the arrangement for obtaining the three standard leads, I, II, III, and lead IV of the precordial or exploring electrode. By the simple additional connections as shown diagrammatically in Fig. 3, the device can be arranged so that one-step movements of the switch will select any of the precordial leads IVT, IVF, IVR or IVL. The switch positions on this instrument give the following contacts: Position I: current taken from the left arm and right arm of the patient is led through the switch box to the positive and negative poles of the electrocardiograph machine, giving lead I. Position II: current from the left leg and right arm is led through the switch giving lead II. Position III: current from the left leg and left arm gives lead ,III. Position IVT: the current from the precordium, or chest of the patient, is paired with the zero potential of Wilson. This zero potential is obtained by leads from the left arm, the right and left legs of the patient, each going through a 5,000 ohm noninductive resistance to a central point which acts as the indifferent point in lead IVT. At this central point, termed the central terminal, a. potential is produced that is so near zero throughout the heart cycle that it may be so considered without encountering serious error. Position F gives lead IVF with current from the precordium, or chest, paired with current from the left leg. Position R gives lead IVR, with current from the chest paired with current from the right arm, and position L gives IVL with current from the chest paired with current from the left arm.

In the multiple patient instrument, four electrodes are attached to the patient; three to the usual extremities and one, a precordial or exploring electrode, to the precordium. Each electrode may be connected to a four-prong polarized plug by a four conductor cable or to regular plug-in connectors as shown in Fig. 10. Any number of patients (in this case four) may be so connected. Each plug is inserted into a polarized plug-in connector or jack on the left-hand side of the switch box. This switch box has two control switches. the patient whose record is to be taken at the moment. The second switch (B) (Figs. 9 and selects any one of the four leads which it is desired to record from the electrodes connected to a patient. On the right hand end of the switch box is a polarized jack or plug-in connection in which is inserted a plug connected to two wires leading directly to the electrocardiograph. Any two lead wires of the electrocardiograph may be connected to the plug with due regard to polarity. The corresponding lead is then selected by the lead switch on the control panel of the electrocardiograph.

With the switches used in the instrument, there are a suflicient number of contact points so as to make it possible to add more patients if so desired.

Referring to Fig. 1, the numeral l8 indicates an electrocardiograph provided with leads II and I2 which are connected to the terminals l3 and I4 of a selector I5 shown in Figs. 2, 6 and '7.

The selector l5 which is mounted within a housing It is of the rotary type and is constructed with a disc shaped index base l1 having laterally projecting ears l1, and a plurality of switch bases or plates l8, I9, and 2| formed of insulating material and provided with laterally pro- Jecting ears l8, I9, 20' and 2| drilled to receive bolts 22.

The index :base l1 and the switch bases I8, I9, and 2| mounted upon the bolts 22 are spaced from each other by sleeves 23;

The index base is provided centrally with a collar 24 having a flange 25 adapted to form a seat and a threaded portion which is adapted to be fitted into an opening in the front wall of the housing l8 and retained therein by means of a nut 25. The index base I1 is provided with circumferentially spaced raised portions 21 over which rollers 28, attached to the opposite sides of an index arm 29, pass, as will be further described.

Within the sleeve member 24 which is attached to the index plate I1 is rotatably mounted an indicator shaft to which is rigidly connected a turning knob 3| provided with a pointer 32 which is adapted to move over a dial 33 attached to the housing Hi. The end of the shaft 38 is squared to fit a central opening in a turning disc 34.

The turning disc 34 is provided with a curved projection 35 which fits into an opening 38 in the index arm 29 so that with rotation of the indicator shaft 38 the index arm which is formed of spring metal is revolved so that the rollers pass over the raised portions of the index plate to indicate a number of contact points marked The first (A) (Figs. 9 and 10) selects on the dial 33. The indicator shaft 38 is slotted to provide for the attachment of a non-circular shaft 31 which projects through centrally located circular openings 38 in the switch bases.

In addition to the large central opening 38, the switch bases l8, I9, 20 and 2| are each provided with a circumferentially arranged row of rectangular openings 39. Within these rectangular openings 39 are fitted a plurality of spring fingers or contact members which are generally designated by the reference character 40. These finears are crimped so that a portion of them may, due to their elasticity, clamp themselves within the openings, as shown in Fig. 6. In the discussion relative to the operation of the device hereinafter to be given, the fingers 40 will each be given individual reference characters. These spring fingers are each provided with semispherically formed ends 4| which are adapted to electrically contact bridging members 42 which are inserted within openings in rotatable discs .43 mounted on the central non-circular shaft 31.

' a lower insulating disc 43 which is supported by brackets 50 which extend from the switch bases and are provided with curved projections which enter openings in the discs 48.

As shown in Fig. 7 the metallic discs 49 are retained in position by the brackets 58, and projections 4B which are crimped in the same manner as the fingers 48 so that the crimped portions may be inserted into an opening in the switch bases l8, I9, 20 and 2|.

The electrodes 5|,-52, 53 and 54 shown diametrically in Fig. 3, and which are attached to the left arm, right arm, left leg and to a precordial electrode on a patient, are connected to the patient leads 5|, 52', 53' and 54' which are in turn connected to the plug-in connectors 55, 56, 51 and 58. From these connectors, selector leads 53, 68, 6| and 52 pass to spring fingers or contacts generally termed 40 on the switch bases.

The connector 55 is connected through the conductor 59 to the contact 63 on switch plate I8, contact 64 on switch plate l9, and to the contact 55 on switch plate 20 through the resistance 56, and through a branch lead 59 to contact 65 on switch plate IS.

The connector 58 is connected through the conductor 68 to the contacts 61 and 58 on switch plate l9 and through the branch lead 69 and resistance 1|] to contact 1| on switch plate I9, and through branch lead 12 to contact 13 on switch plate I 9.

The connector 51 is connected through the conductor Bl to branch leads 14 and'15. The branch lead 14 is connected to contacts 16 and 11 on switch plate l8 and to contact 18 on switch plate IS. The branch lead 15 is connected through resistance 19 to contact on switch plate 2| The connector 58 is connected through conductor 62 to the contacts 8|, 82, 83 and 84 on switch plate I.

The movable contacts which are mounted in the centrally located insulating discs 43 as shown in Figs. 4 and 6 are adapted to rotate with the noncircular shaft 31 and are indicated by the numerals 85, 86, 81 and 88 in the diagrammatic representation in Fla. 3. In this figure the switch tact pin 42, and through a metallic disc 45 to the electrocardiograph, and from the electrocardiograph through a disc 45, through a pin 42 to another spring arm 40, and through a return lead to the electrode on the right arm of the patient.

In the multiple patient selector illustrated by Figs. 8, 9 and 10, the construction and arrangement of the plate members is similar to the single patient device.

In this device, two selectors are used both of which are attached to the front wall of a housing as illustrated in Figs. 8 and 9. Since the construction and operation of these selectors are the same asdescribed above, it will only be necessary to describe their manner of selecting circuits by reference to the diagrammatic illustration as represented in Fi 10. 1

In Fig. 10 the numerals 89, 90, 9| and 92 indicate portions of the side wall of the selector housing 93 in which are mounted four groups of plug connector elements for the reception of plug terminals at the extremities of the patient leads.

In order to trace the circuits connecting pairs of electrodes contacting the patients numbered 1, 2, 3 and 4, inclusive, the electrical connection from the left arm, right arm, left leg and the precordial electrode on each patient will be taken in the numerical order of the patients and traced first to the patient selector.

From patient No. 1: the left arm electrode 96 is connected by the patient lead 91 to the plug connector 98, and the plug connector 98 is connected through conductor 99 to the contact member I of the left arm group of the patient selector, indicated by the letters L.A.; the right arm electrode IN is connected by lead I2 to connector I03, and the connector I03 is connected through conductor I04 to the contact member I of the right arm group of the patient selector, indicated by the letters R.A.; the left leg electrode I06 is connected by lead I01 to connector I08, and the connector I08 is connected through conductor I09 to the contact member III! of the left leg group indicated by the letters L.L.; the precordial electrode III is connected by lead II2 to connector H3, and the connector H3 i connected through conductor II4 to contact member II5 of the precordial group of thepatient selector, indicated by the numeral IV.

From patient No. 2: the left arm electrode H6 is connected by the patient lead II1 to the plug connector I I8, and the plug connector I I8 is connected through conductor I I9 to the contact member I of the left arm group of the patient selector, indicated by the letters L.A.; the right arm electrode IZI is connected by lead I22 to connector I23, and the connector I23 is connected through conductor I24 to the contact member I25 of the right arm group of the patient selector, indicated by the letters R.A.; the left leg electrode I26 is connected by lead I21 to connector I28, and the connector I28 is connected through conductor I29 to the contact member I30 of the left leg group indicated by the letters L.L.; the precordial electrode I3I is connected by lead I32 -to connector I33, and the connector I33 is connected through conductor I34 to contact member I35 of the precordial group of the patient selector, indicated by the numeral IV.

From patient No. 3: the left arm electrode I38 is connected by the patient lead I31 to the plug connector I38, and the plug connector I38 is connected through conductor I39 to the contact member I40 of the left arm group of the patient selector, indicated by the letters L.A.; the right arm electrode I4I is connected by lead I42 to connector I43, and the connector I43 is connected through'conductor I44 to the contact member I45 of the right arm group of the patient selector, indicated by the letters R.A.; the left leg electrode I46 is connected by lead I41 to connector I48, and the connector I48 is connected through conductor I49 to the contact member I50 of the left leg group indicated by the letters L.L.; the precordial electrode I5I is connected by lead I52 to connector I53, and the connector I53 is connected through conductor I54 to contact member, I55 of the precordial group of the patient selector, in-

dicated by the numeral IV.

From patient No. 4: the left arm electrode I56 is connected by the patient lead I51 to the plug connector I58, and the plug connector I58 is connected through conductor I59 to the contact member I60 of the left arm group of the patient selector, indicated by the letters L. A.; the right arm electrode I6I is connected by lead I62 to connector I63, and the connector I63 is connected through conductor I64 to the contact member I65 of the right arm group of the patient selector, indicated by the letters R. A.; the left leg electrode I66 is connected by lead I61 to connector I68, and the connector I68 is connected through conductor I69 to the contact member I10 of the left leg group indicated by the letters L. L.; the precordial electrode I1I is connected by lead I12 to connector I13, and the connector I13 is connected through conductor I14 to contact member I15 of the precordial group of the patient selector, indicated by the numeral IV.

The contact members of the left arm, right arm, left leg, and the precordial groups of the patient selector, are connected electrically to the contacts of the electrode group as follows: contact members I00, I20, I40, and I60 of the left arm group L. A. may be connected selectively, through the rotatable contact member I16 and leads I11 and H1, to the contacts I18 and I19 of the electrode selector; contact members I05, I25, I45 and I65 of the right arm group R. A. may be connected selectively through the rotatable contact member I and leads I8I and I8I to the contacts I82 and I83 of the electrode selector; contact members III), I30, I50, and I10 of the left leg group L. L.may be connected selectively through the rotatable contact member I84 and leads I85, I85, and I98 to contacts I86, I81, and I88 of the electrode selector; and contact members II5, I35,

I55, and I 15 of the precordial electrode group IV may be connected selectively through the rotatable contact member I89 and lead I90 to contact I 9I of the electrode selector.

Contacts I18, I86, I81 and I9I of the electrode selector may be connected selectively through the rotatable contact member I92 and leads I93 to the positive terminal I94 of the electrocardiograph, and contacts I82, I83, I19 and I88 may be connected through the rotatable contact member I95 and lead I96 to the negative terminal I91 of the electrocardiograph.

To illustrate the operation of both the single patient and multiple patient apparatus, a circuit through a pair of electrodes to the electrocardiograph in each device will be described and with this description and the description of the entire wiring system as given above, it will be a simple matter to trace any of the circuits used.

If a circuit through position I of the single patient device is chosen, then from the left arm electrode 5| (Fig. 3) the current will pass through lead 5|, plug-in connector-55, conductor 58 to contact 89, and from contact 88 through switch blade 85 (which represent the metallic disc 45 in Fig. 6) to lead 41 of the electrocardiograph, and from lead 48 of the electrocardiograph through switch blade 85 to contact 81, and thence through conductor 88 to plug-in connector 58 to patient lead 52', and to the right arm electrode 52.

When the pointer is moved to position II, the circuit is from the left leg electrode 53 to terminal contact 18 through switch blade 85, through conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48 to switch blade 88, contact 58, to the right arm electrode 52.

For the third position, or when the pointer is moved to III on the dial, the circuit is from left leg electrode to terminal 11 through switch blade 85, through conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48 to switch blade 98, contact 64 to the left arm electrode 5|.

At position IVT the circuit is from the precordial electrode 54 to contact 8I through switch blade 85 and conductor 41 to the electrocardiograph, and from the electrocardiograph through conductor 48 and respectively through switch blades 86, 81 and 88, contacts 11, 65 and 88 and resistances 18, 58 and 19 to the right arm, left arm and left leg electrodes 52, 5I and 53,

When the pointer is moved to IVF the circuit Patient No. 1, position u (left leg and right arm). From left leg electrode I88 to contact III,

, switch blade I84, contact I88, switch blade I92,

arm)

is from the precordial electrode 54 to contact 82 through switch blade85 and conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48, switch blade 41, and contact 18 to the left leg electrode 53.

When the pointer is moved to IVR the circuit is from the precordial electrode 54 to contact 83, through switch blade 85 and conductor 41 to the electrocardiograph and from the electrocardiograph through conductor 48 to contact 13, and through the switch blade 86 to the right arm electrode 52.

The pointer when moved to IVL completes a circuit from the precordial electrode 54 to contact 84, through switch 85 and conductor 41 to the electrocardiograph, and from the electrocardiograph through conductor 48, switch blade 88 and contact 95', to the left arm electrode 5 I The multiple device as mentioned above is provided with two selectors, a patient selector, having four positions, one for the selection of each of four patients, and an electrode selector having.four positions one for each of four circuits, namely, I from the left-arm and right arm electrodes, 11 from the left leg and right arm electrodes, III the left leg and left arm electrodes, and IV the precordial and left leg electrodes.

The circuits for the I, II, III and IV positions of patients No. 1, No. 2, No. 3 and No. 4 are as follows:

Patient No. 1, position I (left-arm and right arm). From left arm electrode 96 to contact I88, switch blade I18, contact I18, switch blade I92, contact I94 to electrocardiograph. From contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I82, contact I82, switch blade I 88, contact I83, contact I85, and to right arm electrode I8I.

Patient No. 1, position III (left leg and left From left leg electrode I85 to contact H8, switch blade I84, contact I81, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I88, to left arm electrode 98.

Patient No. 1, position IV (precordial electrode and left leg). From precordial electrode III to contact II5, switch blade I89, contact I9I, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I88, switch blade I84, contact I I8 to left leg electrode I88.

Patient No, 2, position I (left arm and right arm). From left arm electrode I22 to contact I28, switch blade I16, contact I18, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I88, contact I25 to right arm electrode I2 I.

Patient No. 2, position II (left leg and right arm). From left leg electrode I26 to contact I88, switch blade I84, contact I88, switch blade I82, contact I94 to electrocardiograph. From electrocardiograph to contact I 91, switch blade I92, contact I83, switch blade I88, contact I25 and right arm electrode I2I.

Patient No. 2, position In (left leg and left arm). From left leg electrode I26 to contact I38, switch blade I81, switch blade I92, contact I84 t0 the electrocardiograph. From the electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I28, to left arm electrode IIG.

Patient No. 2, position IV (precordial electrode and left leg). From precordial electrode I3I to contact I35, switch arm I89, contact I9I, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I88, switch blade I84, contact I38 to left leg electrode I28.

Patient No. 3, position I (left arm and right arm). From left arm electrode I42 to contact I48, switch blade I16, contact I18, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I88, contact I45 to right arm electrode I4I.

Patient No. 3, position II (left leg and right arm). switch blade I84, contact I86, switch blade I82, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I88, switch blade I88, contact I 45 to right arm electrode I4I.

Patient No. 3, position III (left leg and left arm). From left leg electrode I48 to contact I58, switch blade I84, contact I81, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I48 to left arm electrode I36.

Patient No. 3, position IV (precordial electrode and left leg). From precordial electrode I5I to contact I55, switch blade I89, contact I9I, switch blade I92, contact I94 to electrocardiograph. From electrocardiograph to contact I91, switch From left leg electrode I46 to contact I58, I

blade I92, contact I88, switch blade I84, contact I56 to left legv electrode I46.

Patient No. 4, position I (left arm and right arm). From left arm electrode I56, contact I60, switch blade I16, contact I18, switch blade I92, contact I94 to the electrocardiograph. From the electrocardiograph to contact I91, switch blade I92, contact I82, switch blade I80, contact I85 to right arm electrode III I.

Patient No. 4, position II (left leg and right arm). From the left leg electrode I86 to contact I18, switch blade I84, contact I86, switch blade I92, contact I94 to the electrocardiograph. From the electrocardiograph to contact I91, switch blade I92, contact I83, switch blade I88, contact I65 to electrode I6 I. Patient No. 4, position III (left leg and left arm). From left leg electrode I68 to contact I18, switch blade I84, contact I81, switch blade I92, contact I94 to the electrocardiograph. From the electrocardiograph to contact I91, switch blade I92, contact I19, switch blade I16, contact I40 to left arm electrode I36.

Patient No. 4, position IV (precordial electrode and left leg). From the precordial electrode I1I to contact I15, switch blade I89, contact I9I, switch blade I92, contact I94 to the electrocardiograph. From the electrocardiograph to contact I91, switch I92, contact I88, switch blade I84, contact. III! to left leg electrode I66.

Although in the foregoing certain elements have been described as best adapted to perform the functions allotted to them, nevertheless it is to be understood that certain changes may be resorted to without departing from the spirit and scope of the invention as disclosed in the appended claims.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination with an electrocardiograph, a selecting device comprising, a patient selector provided with contact members electrically connected with electrodes attached to a plurality of patients, and a contact selector adapted to selectively contact said contact members; and an electrode selector provided with contact members connected electrically with said contact selector, and an additional contact selector connected with the leads of an electrocardiograph and adapted to selectively contact the contact members of said electrode selector, whereby electrodes attached to any of the patients may be selectively connected with the leads of the electrocardiograph.

2. In combination with an electrocardiograph, a selecting device comprising a patient selector provided with circularly arranged contact members electrically connected with electrodes attached to a plurality of patients, and a rotatable contact selector adapted to contact said contact members; an electrode selector provided with circularly arranged contact members connected electrically with said contact selector, and a rotatable contact selector connected with the leads of an electrocardiograph adapted to contact the contact members of said electrode selector to selectively establish circuits through the electrodes and the leads of the electrocardiograph.

3. In combination with an electrocardiograph, selecting devices comprising, a patient selector including a plurality of stationary contact members electrically connected to patient electrodes, and movable contact members adapted to selectively contact any of said stationary contact members; and an electrode selector including a plurality of stationary contact members electrically connected to the stationary contact members and the movable contact members of said patient selector, said electrode selector being provided with movable contact'tmembers connected electrically with an electrocardiograph and adapted to selectively contact any of said stationary contact members of said patient selector.

4. In an apparatus of the class described for group examination of a series of patients, the combination with an electrocardiograph machine including its positive and negative electrodes; of electrode connector means, a plurality of patient electrodes attached in groups to said connector means, each electrode group including a precordial and a series of limb electrodes adapted to be operatively associated with one of said patients, the respective groups serving to connect simultaneously a series of patients with said connector means, a patient selector permanently connected with said connector means and operable for selecting one of said patients and the electrode group associated therewith, and switching means in electrical relation with the patient selector and with the positive and negative electrode terminals of said electrocardiograph machine for establishing electrocardiographic leads from the patient and electrode group selected by said patient selector, to said electrocardiograph machine.

5. In an apparatus of the class described for group examination of a series of patients, the combination with an electrocardiograph machine including its positive and negative electrodes; of electrode connector means, a plurality-of patient electrodes attached in groups to said connector means, each electrode group including a precordial and a series of limb electrodes adapted to be operatively associated with one of said patients, the respective groups serving to connect simultaneously a series of patients with said connector means, a patient selector permanently connected with said connector means and operable for selecting one of said patients and the electrode group associated therewith, and switching means in electrical relation with the patient selector and with the positive and negative terminals of said electrocardiograph machine for connecting a pair of electrodes in the electrode group selected by said patient selector with said electrocardiograph machine.

MAJOR S. WHITE.

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