THE DIFFERENCES BETWEEN FLEXIBLE MONAURAL STETHOSCOPES AND CONVERSATION TUBES

THE DIFFERENCES BETWEEN FLEXIBLE MONAURAL
STETHOSCOPES AND CONVERSATION TUBES By Erik Soiferman and Eric Rackow

Through the course of my collecting, there is one issue that frequently arises and causes confusion. This issue is the differences between flexible monaural stethoscopes and conversation tubes. Conversation tubes are frequently marketed as stethoscopes, most likely not with intent of deception, but rather because there has been no real research done to differentiate the two. The fact is, that flexible monaural stethoscopes are quite rare, while conversation tubes are relatively common. This article is set forth to provide a basic history and understanding of the differences between stethoscopes and conversation tubes. However, it should be kept in mind while reading this piece, that there were many variations in the manufacturing of these items, and thus, the principles discussed here should not be looked upon as 'hard-and-fast rules,' but rather as a guideline for determining which item you have.

The conversation tube was first patented in 1819 by Johann A. Duncker. He produced a very short tube of leather. This piece connected to another, longer tube which varied in length between 5 and 10 feet. To the end of this was attached a large metal cup (later models used ivory instead of metal). Albert Burkhardt-Meriam (1843-1886) stated that to improve this piece, the speaking bell should be cut at an angle and made of vulcanite. This would allow the most surface area or reflection of sound through the tube.

The conversation tube took over for previous methods of enhancing sound, which are not discussed because they are outside the realm of this paper. They used the premise that by placing the speaking piece close to the mouth, the speaker was able to use normal tones and volume, and thus carry clearer sound and not damage the listener's sensitive ears. Previous methods required the speaker to yell into a funnel, which caused distortion of the voice.

The conversation tube became relatively uniform in the way it was manufactured. The original ideas called for an ear-piece of ivory or gutta-percha which connected to a spiral wire or gutta-percha coil, which was covered with silk, wool, or even leather. This allowed the piece to be folded and carried in the pocket. The length of these pieces varied greatly. They were called to be at least two feet in length, with some measuring up to five feet. Most of the conversation tubes measured between 36 and 48 inches (three to four feet).

On the contrary, flexible monaural stethoscopes were not long at all, usually less than 24 inches (two feet). While the idea behind the two items was virtually the same, they were used differently. Nevertheless, flexible stethoscopes were sometimes longer than some conversation tubes.


A short conversation tube measuring 14 inches long, made by Aloe, circa 1895.	Arnold's Flexible stethoscope measuring 28 inches long, circa 1890.

One of the major reasons for the acceptance or decline of stethoscopes throughout history has been their portability and ease of use for the physician. Stethoscopes that were cumbersome or uncomfortable were quickly forgotten for better, more convenient models. The major difference between the flexible stethoscopes and conversation tubes, therefore, is in the convenience of use for the examining physician. Since physicians did not permit patients to hold the chest pieces on themselves during the examination, the length of useable tubing was limited to the length of the examiner's outstretched arm. It was proven back in Laennec's time that the shorter the distance sound must travel, the more clearly it is conveyed. Tubing that was still coiled was wasted and took away from the sound. Keeping this in mind, flexible stethoscopes were usually made no more than two feet in length, and most are even much shorter (12 to 18 inches).


Goldingbird's flexible stethoscope with flat earpiece and made of wood, circa 1840.	Flexible stethoscope with insertable earpiece and made from pewter, circa 1835.

The photo shown below is a unique Piorry Flexible Stethoscope used for auscultation, circa 1835. The Piorry stethoscope was designed by P.A. Piorry as a monaural stethoscope with an ivory chest piece over the chest bell and an ivory ear piece. The ivory chest piece also served as a pleximeter for percussion. This adaption inserts a flexible tube (instead of the monaural wooden stem) between the typical ear piece and chest bell.

Flexible Piorry Stethoscope, circa 1835.

As seen above, another difference is in the ear-pieces. The ear-pieces of a stethoscope was generally a short, straight knob, as seen above, while that of a conversation tube tended to be longer and either curved or bent at a 90 degree angle. This was best suited for both pieces, because the physician was usually crouched in front of their patient to listen to the heart, while the person using the conversation tube could be in any position and be comfortable with the speaking end being moved anywhere around them. there were, of course, exceptions to this rule.

Some ear-pieces consisted of flattened discs which were slightly concave, designed to fit over the ear, rather than in the canal. This was the case in Golding-Bird's model. These pieces were used in both stethoscopes and conversation tubes, although the round flat ear-pieces of stethoscopes tended to be smaller.

Stethoscopes were used as a diagnostic instrument by physicians. Conversation tubes, on the other hand, were used by the general public. This allowed for a greater diversity in the design of conversation tubes. The speaking-pieces, for example, were made of almost any type of material, in almost any size imaginable. In fact, the most famous manufacture of conversation tubes, the Rein Company, designed their tubes with ornate ivory ear-pieces, and bright, intricately woven tubes. The speaking bells were made of vulcanite, or, for their upper-class customers, silver. Stethoscopes tend to have a uniform chest-piece that can be made to fit securely on the chest.

Sometimes there were stethoscopes that looked exactly like conversation tubes. It is possible that the same item may have been marketed as both a stethoscope and a conversation tube.


Flexible stethoscope with rubber cushion or converstaion tube, circa 1850.	Conversation tube made by Luer, circa 1850.

The piece below is very interesting in that it combines the binaural ear piece of a stethoscope with a very long tube and wide bell charcteristic of a conversation tube. In fact, this piece is neither a stethoscope or conversation tube, but rather a "re-educative binaural tube to enable the patient to read or speak to himself and thus stimulate the dormant auditory centre by natural means of the voice" in order to treat middle ear deafness (Mayer & Phelps, circa 1931)

Re-educative binaural tube, Mayer & Phelps, circa 1931.

This article was designed to help properly identify the instrument in your possession. As mentioned before, conversation tubes are frequently marketed as stethoscopes. There is no way to tell that a tube was not used as a stethoscope at some point, only to say that it's primary purpose was for aiding the hearing-impaired. Flexible monaural stethoscopes are quite rare, while conversation tubes are not. Generally speaking, if you have a piece that is greater than 18 inches to two feet in overall length, you have a conversation tube. If you have a piece with an ornate or large end piece made of horn, metal, or any material other than vulcanite or gutta-percha, you most likely have a conversation tube. If your ear-piece is long and curved, rather than a short (one to two inch or less) straight piece, you most likely have a conversation tube.

These are general guidelines and are not intended to cover every piece ever made.
If you have any questions please do not hesitate to CONTACT us.

References

Bennion, Elisabeth. Antique Hearing Devices. Vernier Press (London), 1994

Benion, Elisabeth. Antique Medical Instruments. Southeby's Publications (London), 1979

Davis, Audrey B. Medicine and its Technology. Greenwood Press (London and Connecticut), 1981

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