Early Stethoscopes -- Monaural and Binaural
Monaural Stethoscope, Cedar and ivory, ca. 1850s (left)
This monaural stethoscope is a solid wooden cylinder with a drilled center that could be unscrewed for carrying in the pocket. At one end, a chest piece auscultated the heart and when removed, the large opening was for listening to the lungs. By the 1850s, the monaural stethoscope was a mainstay of the physical examination.

In 1816, Dr. Rene Laennec, an expert in chest diseases, was examining a young woman with heart problems. Painfully shy, he could not bring himself to press his ear to her chest, the only known method of auscultation. Remembering (a law of physics) a childhood trick of scratching the end of a log with a pin, a sound that would be transmitted loud and clear to the other end of the log, he made a "log" by rolling sheets of paper into a cylinder. Laennec recalled applying one end of it to the region of the heart and the other to his ear, and was surprised to find that he could perceive the action of the heart in a manner much more clear and distinct. This led to the intervention of Laennec's monaural stethoscope in 1819. On the basis of his knowledge of normal and abnormal breath sounds, Laennec could diagnose bronchitis, pneumonia, and most importantly, tuberculosis, a prevalent disease that claimed many lives at the time. Ironically, Laennec himself died of tuberculosis in 1826.

Cammann's Binaural Stethoscope, ca. 1852 (right)
The monaural stethoscope became obsolete by the 1860s with the invention of George Cammann's binaural stethoscope in 1852. The instrument is a monaural, bell-shaped chest piece with two long air conduction tubes that provided an increase of sound simultaneously in both ears. This original 1852 Cammann binaural stethoscope's ear knobs are made of ivory, and the bell chest a piece of ebony. It is inscribed with both Cammann's and Bowditch's names.