A short history of stethoscopes

Today stethoscopes are a typical fixture around doctors’ necks. They are commonly used to listen to the sounds of the heart and lungs as well as the flow of blood during blood pressure readings.

The practice of percussion and immediate auscultation were popular in physical examinations by the early 1800s. In immediate auscultation, physicians placed their ear directly on the patient to observe internal sounds. A French physician named Rene Laennec (1781-1826) was a firm believer in this method of diagnosis. He worked to refine the auscultation procedure and link the sounds with specific physiological changes in the chest.

Immediate auscultation could be an awkward procedure, particularly for female patients.  In 1816, Laennec found himself in one of these situations. He rolled a few sheets of thick paper into a tube shape and applied the tube to the woman’s chest instead of his ear. Later, he made a more durable instrument out of wood and called it the stethoscope. It was a monaural model that consisted of one tube and was used on one ear.

monaural stethoscope, c1890

The first practical bi-aural stethoscope was made in 1851. Flexible tubing is required to make a stethoscope that allowed physicians to use both ears. While many physicians readily adopted monaural stethoscopes, the bi-aural stethoscopes were met with some skepticism. Doctors worried about hearing imbalances caused by using both ears instead of one. For this reason, many doctors continued to use monaural stethoscopes into the early 1900s.

Camman's biaural stethoscope, c1890-1900

The stethoscopes used today are very similar to the ones used in the 1930s. New materials such as flexible rubber, stainless steel, and tygon make them lighter and easier to use. The bells (the end of the instrument applied to patient’s body) have also become flatter. The application of electronic amplifiers to the stethoscope provided the next major modification. These stethoscopes amplified the sound heard by the physician and were capable of filtering high pitched tones in order to make faint tones louder. Some electronic models could provide visual or audio recordings that could be used in training or consultation as well.

Maico Stethetron, c1948

The stethoscope is one of the medical instruments whose development has been dependent on the invention of new materials such as rubber and stainless steel. The sounds the stethoscope produces has been aided by the better understanding of the relationship between anatomy and the laws of physics. Not only did doctors need to understand how to efficiently transmit sound through tubes, they also need to understand how sound waves reacted in the various tissues of the body. These are some of the issues explored in our upcoming exhibit “Tools of the Trade: The history of medical instrumentation.”

Early pharmaceutical tools

Before the industrial production of medicines, all syrups, ointments, pills, and salves were made by hand- often by a trained apothecary or pharmacist. Over the years, specialized tools were developed to assist these specialists in making a variety of medicines. Mortars and pestles were used to grind, pulverize, and mix herbs and powdered medicines. They were made of a wide variety of materials including stone, iron, marble, brass, bronze, glass, or even wood. Mortars in the 17th century were highly decorated. Their use in pharmacies was so central that they became a symbol of the trade. In the mid-1800s, “drug mills” replaced the labor-intensive mortar and pestle to grind or mix large quantities of medicine. Some pharmacists may have used domestic spice or coffee grinders for smaller jobs as well.

brass mortar and pestle with pill tile

Pile tiles, like the one seen behind the mortar and pestle in the photograph, were often made of wedgewood or crockery. They were well glazed to provide a smooth and impermeable surface. Some of these tiles were marked for measurement, others were decorated with professional seals or advertisements. They could be used in conjunction with a small spatula to mix, roll, or divide small quantities of pills.

Pills, or lozenges, have been made by hand (with or without pill tiles) for centuries. For example, the ancient Greeks on the island of Lemnos mixed herbs and other medicines with packed earth to make pills. They might have made these pills with their hands or used specialized tools. Another common and simple technique for ingesting powdered medicine was to dissolve or suspend it in water. However, this was unpopular because many solutions had a bad taste.

“Pill machines” were invented in Germany around 1750 to assist pharmacists in making several standardized lozenges at a time. Some machines made as many as 50 pills, but the more popular machines made 18 to 24. At first they were made of wood, but later parts of the machine were made out of brass. After the pill “mass” was created by mixing the medicine with other non-active ingredients, it would be rolled out to an even thickness using the flat board and a rolling pin. The pharmacist could then use the grooved parts of the machine to mold the pills into rounded shapes on both sides. When the mass dried, the pills could be broken along the lines of the grooves, creating smooth, identical forms. Some pharmacists also used a “pill finisher” to coat the lozenges with gelatin, varnish, or fine talc powder. Pill machines were made and used in the United States until about 1930.

wood and brass pill machine

These pharmaceutical tools are part of the upcoming exhibit entitled “Tools of the Trade.” In this exhibit, visitors will learn more about the evolution of medical instruments from denistry, optometry, gynecology, otolaryngology, and other fields. It opens in Winter 2009!