An Ear to the Chest: An Illustrated History of the Evolution of the Stethoscope
Authors: Arthur Hollman
Journal: Journal of the Royal Society of Medicine (2002)

It was Dr Blaufox's interest in the history of measurement of blood pressure that led him to acquire an important collection of stethoscopes and stimulated him to write about their evolution. As the title indicates his book is very well illustrated, with 28 figures in the text and good photographs of 88 stethoscopes from the author's collection. The numerous illustrations make it a very useful addition to the published work, though the price is surprisingly high. Ten chapters describe the various stages of evolution of the stethoscope and offer a comprehensive collection of references.

Some historians decry the seminal role of the individual in making important discoveries, maintaining that it is the overall situation at the time which is the determining factor for progress in science and medicine. They choose to ignore that innovative men and women have personally initiated great advances. Such an advance was made by Theophile Rene Hyacynthe Laennec on 13 September 1816 with his invention of the stethoscope which almost overnight transformed the desultory application of an ear to the chest (immediate auscultation) into the widely used discipline of mediate auscultation. The famous occasion when he rolled up a quire of paper and listened to the chest through it was luckily witnessed and recorded by a British doctor, Augustus Granville. The roll of paper was soon replaced by a wooden cylinder and this new instrument was quickly adopted in Europe, Britain and America, with the backing of good studies relating the sounds heard in the chest and the heart to the pathology as found post mortem. It may seem surprising that auscultation had not been used widely beforehand, because Hippocrates had mentioned the succussion splash in the chest and William Harvey in 1628 noted that ‘there is a beating which is heard within the breast’. Clearly an instrument was needed to catalyse the development of auscultation and it was not long before modifications of the Laennec model and completely new types of stethoscope were produced.

The monaural model of Laennec was not ideal, and indeed was described by an American doctor as ‘the objectionable European instrument’, but remarkably its many modifications persisted for nearly 100 years and as late as 1912 an instrument catalogue showed 78 monaural types as opposed to 53 binaural. However, there was an early urge to produce a binaural instrument and CJB Williams of London made one in 1829 using two bent lead pipes. Progress depended on getting a flexible material for the tubing; although vulcanization of rubber was achieved in 1939 it was not until 1888 that Dunlop produced the pneumatic tyre. Nevertheless, eager inventors were at work. CW Pennock of the USA made one of flexible brass tubing in 1844, others used woven silk impregnated with unrefined rubber (caoutchouc), and A Leared produced one of gutta percha for the 1851 Great Exhibition. But Dr Blaufox is clearly correct when he maintains that the first truly practical binaural device, one which looks like 20th century models, was that of George Cammann of New York, in 1856. It was naturally desirable to convey the sounds directly into the ear and he used ivory knobs. The ingenuity displayed in new designs is well seen in this book, when one looks at for example Alison's differential stethoscope which had two chest pieces allowing sound from two different areas of the chest to be heard at the same time.

But the most original and thoughtful change in design was the invention of the diaphragm type of chest piece in 1894 by Robert Bowles of Massachusetts. The flat surface gave good contact with the chest and was easily applied to the elbow for measurement of the blood pressure. Its superiority to the bell for high-pitched noises was only later recognized. It was left to Howard Sprague of Boston to introduce the final important modification by combining a diaphragm and bell in one chest piece in 1926. The Sprague—Bowles stethoscope became the preferred instrument, though many doctors continued to use a bell only, or sometimes a diaphragm, well into the 1950s.

As Dr Blaufox points out there have been numerous modifications over the years and he has done a good job in summarizing a complex matter. Without being parochial I suggest that he could have included the design made by Aubrey Leatham at St George's Hospital, London, in 1955 which uniquely had a bell with two components, large and small. The Littmann stethoscope of 1961 was essentially a redesign of the Sprague—Bowles, but its lightness and ease of use has made it the standard model in current use. Dr Blaufox ends his book with a note of deep regret that the emergence of modern imaging techniques has led to a neglect of clinical examination. The stethoscope is being put aside by devices which obviate the basic skills of history taking, observation and examination.