THE BINAURAL STETHOSCOPE

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In the early 1850's there was a rush of designs for a new stethoscope that used both ears. This new
'Bi-aural' or 'Binaural' instrument was felt to be the future of auscultation. Interestingly enough,
the idea for a binaural stethoscope was first introduced in 1829, just a few years after Laennec's
original instrument. The idea belonged to Nicholas Comins, who devised a stethoscope that he
described as "a bent tube" that had several hinges, allowing the physician to not have to assume
uncomfortable positions during the examination. He offered the suggestion of making his
instrument binaural, and may have, as there are only sketches of his instrument. However, there
are no known examples of this piece in any collection.

The first commercially marketed model was that of Dr. Marsh of Cincinnati in 1851. His model
contained the first recorded diaphragm chest piece. However, it proved bulky and cumbersome,
and quickly faded. The diaphragm would not re-surface for about 50 years.

In 1855, Dr. George Cammann of New York produced the first recognized usable binaural
stethoscope. He was working as a physician at the Northern Dispensary, and had seen Marsh's
model. He also had a model with two ear-pieces from Europe, which as designed for two people to
listen at the same time. Cammann did not claim to have the original idea for a binaural
stethoscope, only to have perfected it.

Cammann had some help in designing his stethoscope, and, interestingly enough, never put his
name on the piece. The stethoscope was named 'Cammann's' by the manufacturer of the original,
George Tiemann.

Cammann's model was made with ivory earpieces connected to metal tubes. These were held
together by a simple hinge joint, and tension was applied by way of an elastic band. Attached to
these were two tubes covered by wound silk. These converged into a hollow ball designed to
amplify the sound, and attached to to the ball was a conical, bell chest piece.

As was the case with Laennec's model, Cammann's was not embraced  completely either for quite some time. It was not until Austin Flint (who had previously spoken against the binaural in 1856)endorsed it in 1866 that it became widely used. The stethoscope was also used as a status symbol.It was sometimes sold as a set, with a pleximeter and percussor. This one (pictured right), made of ivory, is especially nice. (Photo courtesy of the Mutter Museum)

There were many different modifications to Cammann's original instrument. Scott Alison came up
with a 'Differential Stethoscope' that consisted of two independent chest pieces, and
was designed to allow the listener to compare the sounds of two areas of the chest.
This instrument was also found to be impractical because it muffled certain sounds.
Most references list this piece as circa 1885, but it was actually first illustrated in the
John Weiss & Son catalog in 1863.

Several physicians came up with their own ideas for stethoscopes using materials that were
commonly found in a physician's office. For example, in 1884, E. T. Aydon Smith described a
stethoscope he invented:

"..the chest-piece of which is formed by a pair of

ear-specula. the tubes are Jaques' India-rubber

catheters, and the ear-pieces those of an otoscope."

He designed his instrument to be used as a simple binaural, a differential stethoscope (by using
one of the ear-pieces and chest-pieces for each ear), a tourniquet (by wrapping the rubber around
the arm), and, also as a urinary catheter for both males and females. Quite a diverse instrument!!

The next improvements began around 1880, and focused on the tension mechanism to hold the
ear-pieces to the head of the physician. There was a design of a spring-tension mechanism which
had a screw that could be turned to open or close the ear-pieces. The first of these new models was
KNIGHT'S model, which had a characteristic design on the poles that attached to the ear-tubes.
The Charles Truax catalog of 1890 states:

"Knight's stethoscope does not differ materially from the pattern of Cammann...The principal
change is in the form of the spring, which in this case is spiral, acting on two levers in the form of
a toggle joint."
(p. 51).

The screw mechanism became a great success, and would be included in the models that would
follow for many years. However, there was still a desire to improve the sound conduction through
the tubes. Around 1882, Bartlett designed a stethoscope that used metal ear-tubes with the silk 
covered rubber tubes leading to a wooden chest piece. This model was also called
"Bartlett's Laennec" stethoscope, and was an ingenious design. Truax describes Bartlett's Laennec
model;

"The Laennec stethoscope, devised by Bartlett, belongs to the heavier class of stethoscopes, the
instrument throughout being stronger that those of the ordinary Cammann pattern....A heavy
spring, somewhat similar to the pattern of Knight..."(p. 52)

In 1885, Charles Denison came out with an entirely new model, based on Bartlett's. His was based
on the idea of funneling sound to the ears, much like the monaurals. His earpieces were made of
hard rubber which led into woven tubes and a large chest piece. It came with three interchangeable
chest pieces for hearing different types of sounds. The tension between the earpieces was
accomplished by a clever screw mechanism.

Denison's model was widely accepted. So widely, that many makers began
marketing inferior pieces of the "Denison Stethoscope." Denison became outraged
at the poor quality of stethoscope being manufactured with his name. He delivered
a powerful speech in which he stated precisely how his stethoscope was to be made,
condemned the makers of poor instruments, and praised one American company
for their quality craftsmanship.

As Denison's was becoming popular, more improvements to Cammann's original design began tosurface. Most of these did away with the resonating bell in favor of longer tubes, such as Davis' modification, which is pictured to the right.  Although the Cammann was still being produced until around 1895, most physicians had moved on and were using other, more convenient models.

Convenience came in several ways. I have already mentioned the longer tubes, which added more
flexibility, but other methods were used as well. Around 1880, Lynch's stethoscope was marketed,
which folded onto itself and thus greatly reduced it's length. Sheppard's model (1890), by contrast,
folded the earpieces together, reducing the width of the instrument.

This piece is another Cammann variation called "Leared's Stethoscope"   

Another modification was Dr. Cammann's modified instrument (D.M. Cammann, M.D., not the
same as the original), incorporated a chest piece with a rubber ball, which was used as a suction
cup to apply it to the chest. This would leave the hands free to percuss to chest. It was found to be
of little value to the untrained ear.

The next landmark improvement was the invention of the 'Ford's Bell' chest piece in 1885. This
simple model was made of steel with either gutta-percha, ebony, or even ivory at the base. It
funneled sound into two tubes, usually made of rubber, which led to the earpieces. Below are two
examples of Ford's bell stethoscopes:

Below are two other examples of early bianural stethoscopes:

There were also other stethoscopes that were being used. Some of them were relatively strange as
we look at them today. The Phonendoscope, for example, invented by Bazzi and Bianchi in 1894,
was a small circular unit with two membranes placed next to each other. To this was attached a
small steel solid tube which had a small gutta-percha chest piece. There were two long runner
earpieces that attached to the top of the unit. It was totally collapsible and measured only three
inches in diameter. The idea was that the small chest piece could fit between the ribs and convey
better sounds.  While the Phonendoscope was marketed in America exclusively by the G. Pilling Company of Philadelphia, it was also being used in other countries, such as this French model.

Another example of this type of stethoscope is the WINCARNIS STETHOSCOPE. This is a very intriguing piece, The two small discs are interchanged and placed against the small plastic diaphragm, allowing the listener to very the loudness and quality of the sounds conveyed. The earpieces, made of ivory, are plugged into the top of the piece in the same fashion as the Phonendoscope. A very unusual idea. There is only one other known example of this piece in the world, which is located in the London Science Museum.

Marsh's Stethoscope, or Marsh's Stethophone, is a very interesting invention. It comes with a
small dial on the back which has a pointer and the letters 'L,' 'S,' and 'W' engraved on it. These
stood for 'Loud,' 'Soft,' and 'Weak,' respectively. The examiner would dial in the type of sound he
was listening to in order to be able to hear it better. 

This piece  is very interesting in that it combines the binaural stethoscope with a 

very long tube and a bell. The tube is long enough to be used as a conversation tube, but this is, in fact, a stethoscope. Photo courtesy of Alex Peck.



The bell chest piece was great for hearing the low-pitched sounds of the chest, however, there was
the need to hear the higher pitched sounds; Enter the diaphragm chest piece. This was a membrane
over the bell that allowed the higher sounds to come through but blocked out the lower ones. It
came to be used around 1910.

The diaphragm became the standard for the modern stethoscope, but some of the early models resembled the older ones, such as this piece, signed "F. Davidson, London," circa 1920. It is made of all metal, and folds like Sheppard's model, and came in a leather case.

I am always interested in acquiring new items for my collection, and am anxious to talk to dealers and collectors. If you have any items for sale, or have any comments, questions, or corrections, please do not hesitate to contact me.