AUSCULTATION, a term in medicine applied to the method of determining, by the sense of hearing, the condition of certain internal organs. Strictly, it should include audition of sounds produced within the body naturally and sounds induced artificially by the physician, but often the term percussion is applied to the last mentioned. In the beginning auscultation was direct only, the physician placing his ear over the heart or lungs, or, in percussion, tapping the part with his fingers. These methods are still followed but in the main some material is interposed be tween the listening ear or the percussing finger and the patient's body. In its modern sense auscultation dates from 1819 when Laennec invented the stethoscope. Some variations from the normal in heart or respiration sounds are associated with special morbid changes so constantly that diagnosis is certain.
The following are simple examples. When the normal heart sounds represented by "lab dup" are replaced by "loove dup" it is evidence that the mitral valve is not closing properly, if replaced by "lab" and a blowing sound in place of "dup" the aortic valve is affected. When the normal slight rustle heard during inspiration and the almost silent expiration are replaced by crackling or snoring sounds there is evidence that the lung contains an abnormal fluid as in consumption or bronchitis. In cases of pneumonia, where the air in the lung is replaced by exuded and coagulated serum, a dull note replaces the normal resonant note on percussion. These examples might be extended indefinitely. One of the most striking instances of the value of auscultation is in the diagnosis of pregnancy. An adult woman's heart beats at the rate of some 7 5 per minute, a foetal heart beats at the rate of 120-140 per minute. (W. S. L.-B.)