1816: The invention of the stethoscope

Figure 2 -- Laennec's Stethoscope (1820). Perhaps it provided some

solice to Laennec that he was diagnosed with consumption using

a stethoscope similar to this. Copyright Science Museum/ Science

and Society Picture Library

The stethoscope is a common tool used to listen to lung sounds.  The ear pieces are inserted into your ears, and the distal end is placed over the patients chest on various locations to listen to a patients lung, heart and bowel sounds.  It's such a common tool that many of us take it for granted.

The process of listening to internal sounds of the body is called auscultation. There are essentially two different types of auscultation:

1. Intermediate Auscultation:  Placing your ear directly on the patient's body
2. Mediate Auscultation: Using a stethoscope to listen to internal sounds of the body

Intermediate Auscultation was first described around 400 B.C.by physicians from the school of Cos, also known as the Hippocratic physicians.  Many simply give credit to Hippocrates, perhaps because he was the most famous physicians of that era.  He wrote the following in De Morbis:

You shall know by this that the chest contains water and not pus, if in applying the ear during a certain time on the side, you perceive a noise like that of boiling vinegar. (1, pages 28-29)

Auscultation was a technique important to Hippocrates because he believed an imbalance of the humors (fluids in the body) were responsible for the various diseases that plagued mankind.  Phlegm was one such humor, and it was produced in the brain.  When an accumulation of phlegm flowed from the brain to the lungs, this caused diseases of the lungs, such as peripneumonia (pneumonia), phthisis (consumption, tubrerculosis), or asthma.

Figure 2 -- Here Laennec is holding his monaural stethoscope,
although he is using the method of intermediate auscultation
to listen to the lungsounds of a patient with consumption.
You can see by this painting how Laennec was so dedicated
to his work that he had no fear getting close to the sick.
In the end, after years of studying tuberculosis, he died of it.

Even while most of what Hippocrates wrote was later adapted by the medical community for the next several thousand years, the act of intermediate auscultation was only used by random physicians.  One of the main reasons it was rarely adapted by physicians was because most patients were gross, as few people were accustomed to regular bathing prior to the 1900s, or better yet, the 1950s.

A second reason why few physicians used intermediate auscultation was because many sick people had contagious diseases, and placing your ear against a sick person's chest greatly increased your likelihood of catching that person's disease. So, it was rarely done.

Starting in the 18th century there was an increased emphasis among the medical community to consider adequately assessing the patient in order to properly diagnose.  There was an increased emphasis on taking a pulse, watching the respiratory rate and rhythm, and taking a temperature.

By 1816 a French physician by the name of Rene Laennec was one of the wold's best expert on diagnosing diseases of the chest, including heart disease, tuberculosis, pneumonia, and asthma.  One method he used, along with those mentioned above, was chest percussion.

This method involved tapping on various areas of the chest, and the sound emitted helped him to diagnosed.  A dull sound might mean there was a build up of fluid in the chest, which may indicated hydropsy, or what we would now call pulmonary edema or heart failure.  It may also indicate pneumoia.  A tympanic sound may indicate emphysema or asthma.

However, on a hot and humid day in 1816 he was asked to help diagnose a very large lady who was sweating profusely.  He tried to do chest percussion, but it was of little use.  He then thought to do intermediate auscultation, whereby he normally places a hanker chief upon his patient's chest and listens to lung sounds. However, this lady was so obese he figured he wouldn't hear anything.  Plus the lady was so gross and disgusting he didn't want to put his head anywhere near her chest.

Of this experience, he wrote:

In 1816, I was consulted by a young woman laboring under general symptoms of diseased heart, and in whose case percussion and the application of the hand were of little avail on account of the great degree of fatness. The other method just mentioned (auscultating with an ear to the chest) being rendered inadmissible by the age and sex of the patient, I happened to recollect a simple and well-known fact in acoustics, and fancied it might be turned to some use on the present occasion. The fact I allude to is the great distinctness with which we hear the scratch of a pin at one end of a piece of wood, on applying our ear to the other. Immediately, on this suggestion, I rolled a quire of paper into a kind of cylinder and applied one end of it to the region of the heart and the other to my ear, and was not a little surprised and pleased, to find that I could thereby perceive the action of the heart in a manner much more clear and distinct than I had ever been able to do by the immediate application of the ear. (1, page 6)

It was in this fashion the stethoscope came to be.  He then set out to perform experiments whereby he would listen to lung sounds of his patients, and when he died he would match the symptoms in life with what he found in death.  It was in this way that Rene Laennec became the first physician to master diagnosis by using mediate auscultaion, or by using the stethoscope.

His first stethoscope was a bit different than the ones we use today, as his was monoaural: it was a cylindrical and hollowed out tube whereby one end was placed against the physician's ear and the other to the patient's chest.  He described it this way:

The first instrument which I used was a cylinder of paper, formed of three quires, compactly rolled together, and kept in shape by paste. The longitudinal aperture which is always left in the centre of
paper thus rolled, led accidentally in my hands to an important discovery. (4, page 7

He initially called his invention le  cylinder.  However, after his colleagues insisted on naming it, and he not liking any of their names, he humbly named it the stethoscope, with stethos coming from the Greek term for chest, and scopium from the Latin term for object for viewing.  

References:

1. Laennec, Rene Theophile Hyacinthe, "A treaties on the diseases of the chest, and on mediate auscultation," translated by John Forbes, 1838, New York, Philadelphia, Samuel S. and William Wood, Thomas Cowperthwaite and Company
   
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