[Laennec and the creation of auscultation signs]

Toward the end of the 18th century, clinical diagnosis in medicine shifted its focus from reliance on symptoms, which translates to subjective experience of illness, to signs, objective manifestations of pathologic changes. Several techniques were developed to elicit signs in clinical practice, and Laennec used them routinely. He palpated and prodded his patients to get an idea of changes in internal organs. He also applied his ear directly to his patient's chest to hear their heartbeat. On one occassion, he was unable to use these techniques and had the happy occurrence of rolling up a notebook to hear his patient's chest. This led him to hear a great number of new sounds. Through detailed observations, he was able to describe, classify, and correlate these sounds with autopsy findings, thus creating a new semiology of chest diseases. In this essay explore how in which Laennec created his instrument and system of signs of chest diseases, and how he was able to transmit his inventions to his colleagues.