Before Laennec, respiratory diseases that we recognize today were often confused, because the heart and lung are locked inside the rib cage. Impressed by the autopsies performed by Xavier Bichat (1771-1802), Laennec maintained the importance of the anatomoclinical method. But he indicated in his early 1820s lectures at the Collège de France that the discovery of auscultation was fortuitous and empirical. Duffin demonstrates that medical discoveries hardly obey an implacable logic, they arise outside of pre-established projects. In this paper, we retrace the chronology and antecedents at the origin of the important medical invention that is the stethoscope.