The stethoscope has been an integral part of the doctor's armoury for more than a century.

BBC World Service's Health Matters programme examines this week whether this mainstay of medicine has a future as new technologies such as ultrasound take over.

The stethoscope allows doctors to listen in to sounds from within the body, amplifying the heart and lungs to pick up murmurs and other potential problems

French physician Renne Laennec invented the stethoscope in the 19th Century - as a matter of preserving patient dignity rather than any great medical breakthrough.

Arthur Middleton, who collects and sells ancient medical equipment at his shop in Covent Garden, London, told the BBC: "Early in Laennec's career he was called to visit a sick young lady - he was wondering how to diagnose her - especially as he knew she was young and quite corpulent."

On his way to the appointment, so the tale goes, he spotted two young boys tapping out messages to each other from either end of a hollow log.

Cardboard breakthrough

When he arrived at the appointment, he asked for a sheet of cardboard, rolled it up, and used it to maintain a proper distance from his patient.

The idea quickly caught on, according to Middleton.

He said: "Most of his young colleagues realised it was a wonderful invention.

"This was because they were working in pauper hospitals - it put them nine inches away from contagious patients."

While the general principle of the stethoscope has changed little since then, its design makes it almost unrecognisable, with modifications to amplify the sound further.

In skilled hands it can diagnose a wide variety of heart and lung conditions, including valve defects and holes in the heart.

The advent of ultrasound allows doctors to check the diagnosis made using stethoscope.

Digital vision

But in the future, the computer age could revolutionise the way that they work.

Carl Leake, from 3M, a major manufacturer of stethoscopes, says that digital technology will improve the quality of the diagnosis.

He said: "I'm not sure that doctors fully hear the sound they think they hear - because quite frankly some of them are of such low-frequency that they are probably inaudible.

"Digital stethoscopes can store sounds - you can play them back again and again, and even slow them down.

"You could send the sound to a colleague, or a consultant for a second opinion."

However, his new-fangled device may have to wait a while before becoming the norm.

Most doctors stick with the listening device that accompanied them through medical school - and will be unwilling to ditch it.

This story is featured in the radio programme Health Matters on the BBC World Service.

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