Dr. Girdner’s Telephonic Bullet Probe. 
(Extract from New York Medical Journal, April 9th, 1887.) 
ON THE DETECTING AND LOCATING OF METALLIC MASSES IN THE 
HUMAN BODY BY MEANS OF THE INDUCTION BALANCE 
AND THE TELEPHONIC PROBE. 
By JOHN HARVEY GIRDNER, A.B., M.D. 
1\/T Y purpose in this paper is to describe the induction 
balance and the telephonic probe, two appa- 
ratuses which are to aid the surgeon in determining, in a 
painless manner, the precise spot at which a leaden bul- 
let is located, or any other metallic substance which may 
trician and inventor, that, with 
tion coils, having a telephone receiver m the secondary 
circuit, he might be able to determine the location of the 
bullet by an audible sound which would be produced in 
the telephone when the balance was disturbed by the ex- 
Fib. I. 
have found a lodgment in the tissues or cavities of the 
human body. The principle of induction in electricity 
is so well understood that any account of it in an article 
of this kind would be out of place ; therefore I shall con- 
fine my remarks to the application of it to purposes of 
surgical diagnosis In the Summer of 1881, during the 
anxious days of the last illness of the late President Gar- 
field, and when the surgeons in attendance had failed by 
every means at their command to locate the assassin’s 
bullet in his body, it occurred to Professor Alexander 
Graham Bell, of Washington, D. C , the well-known elec- 
ploring coils being brought to a point on the surface of 
the body directly opposite to the bullet. Strangely 
enough, this same idea of using the induction balance oc- 
curred to Mr. George M. Hopkins, of Brooklyn, at about 
the same time, and independently of Professor Bell. 
Professor Bell at once constructed an apparatus and took 
it to the White House, and made the experiment on the 
person of the President, but failed to find the bullet, 
owing to the crude character of the apparatus thus hur- 
riedly constructed, together with lack of experience in 
its use, and also to the disturbing influence on the bal- 2 
DR. GIRDNER’S TELEPHONIC PROBE 
ance of a steel mattress under the hair one on which the 
President lay, and the presence of which was unknown 
to the experimenters at the time. 
No other attempt was made to find the bullet in the 
President’s case, as Professor Bell was unavoidably kept 
from further experiment at that time ; hence the location 
of the bullet remained unknown until the autopsy at 
Elberon revealed it. 
It would, doubtless, be of interest to follow the subse- 
quent history of the development of this apparatus to its 
present state, but I shall content myself by saying that 
Professor Bell has now placed at our disposal a highly 
practical apparatus, which, used in connection with his 
other invention—which I have ventured to name the 
telephonic probe, and will describe further on—gives us a 
three inches and a half in diameter by three quarters of 
an inch thick, and the spool on which the wire is wrapped 
is of card-board. These two coils, together with the 
rheotome and battery, it will be seen, are connected by 
wires, forming a complete circuit, marked primary circuit. 
At E and F are coils precisely similar to those shown at 
D and C, and at G is a telephone receiver. The coils E 
and F, with the telephone receiver, it will be seen, are 
connected by wires, and form a complete circuit, marked 
secondary circuit. It will also be observed that the course 
of the currents in the two circuits is in opposite direc- 
tions, as indicated by the arrow-heads. 
Fig. 2 represents the same parts as Fig. 1, except that 
in the latter cut the apparatus is shown in position for 
work—that is, the coils E and F of the secondary circuit 
nearly perfect and almost painless means of determining 
the location of metallic masses in any of the tissues or 
cavities of the human body. 
Fig. 1 shows the essential parts of the induction bal- 
ance. At A is an ordinary bichromate-of-potassium bat- 
tery of six cells; a greater or less number of cells can be 
used, but the best results will, I think, be obtained when 
six freshly filled cells are used. At B is shown a rheo- 
tome ; as an interrupted and not a continuous current is 
required, five or six hundred interruptions per second 
should be had. At C is a small coil of about No. 25 
copper wire, thoroughly insulated. This coil is about 
one inch in diameter by half an inch in thickness, and 
the spool on which the wire is wrapped is of hard rubber. 
At D is another coil of fine insulated copper wire, about 
are laid on the coils I) and C of the primary circuit, so 
that when the current is passed through the primary cir- 
cuit a current is established in the secondary circuit by 
induction, and there is a loud musical sound produced 
in the telephone receiver at G. Now, if the coil F be 
moved about on the surface of the coil C, a position will 
be found for it in which there is a perfect balance estab- 
lished between the two currents, and consequent silence 
in the telephone. 
With this balance established, if any metallic substance 
be brought near to the point marked H, which is the 
centre of the induction area, the balance is disturbed and 
the telephone gives forth a high-pitched musical sound 
which increases or diminishes as the metal approaches 
or recedes from the point H. Now, it is evident that to DR CxIRDNER’S TELEPHONIC PROBE 
3 
make this apparatus available as a means of surgical 
diagnosis, we must arrange to bring the point H in the 
neighborhood of the metallic mass, and thus have a 
means of exploring the whole surface of the body in 
which we suspect a bullet to be lodged. In order to do 
this, the two coils, E and D, which we will call the ex- 
ploring coils, are let into a turned-out space in a block 
of wood and held in position by melted paraffin being 
substance j or, if this is not possible, as nails are used in 
most tables, be certain you know where each nail is located. 
Remove all metal from the operator so far as is possible, 
and know where each piece which remains is located, so 
that allowance can be made if it exerts a disturbing in- 
fluence on the balance. The patient’s teeth should also 
be examined for fillings, if you propose to search for a 
bullet in the neighborhood of the cheek. All these pre- 
cautions being observed, you are ready to begin the ex- 
ploration. Place the telephone to your ear at the same 
time that an assistant holds the explorer at arm’s length 
about twelve inches from the patient’s body. If now you 
hear a noise in the telephone, it indicates that the two 
circuits are out of balance, and you must turn the screw 
in the adjuster (Fig. 6), first one way and then the other, 
until you find the noise in the telephone growing weaker, 
and finally it disappears entirely ; then there is a perfect 
balance. Now take the explorer from the assistant, and, 
holding it at arm’s length, pass it slowly over the patient’s 
body, without pressure, allowing the velvet to barely 
touch the skin, holding the telephone to the ear the 
while ; when the centre of the explorer (Fig. 5), which is 
the centre of the area of induction, reaches a point on 
poured over them and then allowed to harden, as in Fig. 
3, which shows the flat surface of the block with the ex- 
ploring coils A and B in position, and Fig. 4, which 
shows a cross-section of the same. 
After the coils have been secured in their proper places 
by means of the paraffine, a piece of silk velvet is pasted 
over them to give a soft surface for contact with the skin 
in explorations of the body. A handle is next glued on 
the upper surface, and the wires from the coils are made 
to pass out along grooves in its upper and lower surfaces, 
and it is thus called the explorer. (See Fig. 5.) 
The coils F and C, Fig. 2, are called the adjusting 
coils, and are also attached to a block of wood and ar- 
ranged with a delicate screw adjustment for moving one 
upon the other, thus enabling us to obtain a perfect bal- 
ance between the two circuits and perfect silence in the 
telephone. Fig. G shows this screw adjustment. 
To use the apparatus, place the patient on a table with 
the parts exposed in which the bullet is supposed to be 
located, place the table in the middle of the room, and 
have both patient and table entirely free from any metallic 
the skin directly opposite the bullet in the body, the tel- 
ephone announces it by a musical sound, and, as you ap- 
proach or recede from this point on the skin with the 
centre of the explorer, the sound in the telephone in- 
creases or diminishes. This point on the skin should be 4 
DR. GIRDNER’S TELEPHONIC PROBE. 
marked, and we know certainly that if a needle is passed 
directly in at this point at right angles to the skin, it will 
come in contact with the missile. 
We come now to the second apparatus mentioned— 
viz., the telephonic probe, another of Professor Bell’s in- 
ventions. It consists of a plate of polished steel six 
inches long by two inches wide and half an inch thick, 
shown at B, Fig. 7. In one end of this plate is a hole 
from which a small copper-insulated wire leads to a tele- 
point, as at B, and lays the steel plate on this moistened 
surface, and, while an assistant presses it firmly against 
the skin, he places the telephone receiver to his ear, and 
with the other hand thrusts the steel needle into the tis- 
sues at right angles to the surface. The body now acts 
as a battery, with the steel plate and the needle forming 
the two poles, and a feeble, continuous electric current 
passes through the circuit thus formed ; but when the 
needle touches a metallic mass, this current is interrupted 
and a distinct and peculiar “click” is heard in the tele- 
phone, and the distance of the bullet from the surface 
can be read off on the graduated probe. If the needle 
touches bone or any other tissue, no noise is heard. 
This probe can, of course, be used independently of 
the induction balance, and with equally good results, 
when the probe is made to follow in the track of the bul- 
let, and any other metal than steel may be used for the 
probe, provided the plate applied to the surface be of the 
same metal. 
I desire to express my thanks to Mr. 
W. F. Ford, of Hazard, Hazard & Co., 
for the cuts used in this article. 
They are prepared to manufacture 
these apparatuses, and theirs is the 
only place where, to my knowledge, a 
reliable instrument can be had at pres- 
ent. 
120 West 35th Street. 
phone receiver, C. At A is a finely tempered steel needle 
of suitable length, which may be for convenience gradu- 
ated in inches and parts of an inch ; from the eye of this 
needle a second wire leads to the other pole of the tele- 
phone receiver, C. The manner of using this apparatus 
is shown in Fig. 8. The point on the surface opposite 
the bullet having been determined by the induction bal- 
ance, as described above and shown at A, Fig. 8, the 
operator moistens the skin with vinegar at a convenient 
HAZARD, HAZARD & CO., 
Manufacturers, Importers, and Dealers in 
Every Description of Surgical Instruments. 
W. F. FORD, Manufacturer, 
Instrument Maker to Bellevue, Charity, and all other New York City Hospitals ; also, St. Luke’s, New York 
State Woman’s Hospital, and New York Hospital. 
BROADWAY, CORNER 24th STREET, NEW YORK