Auscultation (from a Latin word signifying to listen), the art of detecting diseased conditions by the alterations which they produce in certain natural sounds. By means of a stethoscope applied to the chest the physician can discover any deviation from the normal character of the heart sounds, or of the sounds produced in breathing, and thus a most valuable means of detecting the existence of disease is afforded. Thus the presence of fluid in the chest cavity is in some cases productive of a splashing sound if the patient make a slight movement; this fact was known from the very earliest times, and is alluded to by Hippocrates, and this "succussion," as it is called, is thus the most ancient and venerable of all auscultation signs. The development of the science of auscultation is, however, of quite recent date, and was no doubt in part suggested by the method of percussion which was introduced in 1761 by Auenbrugger of Vienna, To Laennec, a French physician, is due the credit of introducing the stethoscope, and formulating the main doctrines of auscultation (1819). He described the altered character of the breathing sounds produced by solidification, or the formation of cavities in the lung, and the "murmurs" or "bruits" which accompany certain diseases of the valves of the heart. The art of auscultation has, however, progressed considerably since his time, and now forms one of the chief subjects of study in medicine, and is one of the most valuable aids to diagnosis which the physician possesses.