\lȧ-en-ek\, René–Théophile–Hyacinthe (1781–1826),
French physician. Laennec is usually regarded as one of the great clinicians of all time and as the father of chest medicine. A foremost authority on tuberculosis, he established that all phthisis is tuberculous. He described pneumothorax and distinguished pneumonia from the various kinds of bronchitis and from pleurisy. He is also credited with inventing the stethoscope; his primitive device was a wooden cylinder about a foot long. For three years he studied patients' chest sounds and correlated them with the diseases found on autopsy. In 1819 he published his findings in a work on auscultation with the aid of a stethoscope. It was in that work he described Laennec's cirrhosis.