It's 1816.

A 35-year-old doctor by the name of René Laennec

is walking through Paris.

He pauses to watch as two children signal to each other across a long piece of wooden board.

One child holds the board to her ear.

The other scratches the opposite end

sending the amplified sound down the length of wood.

Later, Laennec is called to assess a young woman with a heart condition.

The patient is purportedly quite well developed

and Laennec expresses some hesitation

in pressing his ear directly against her chest.

Remembering the children with the board,

Laennec, in a moment of vision and dignity,

tightly rolls a sheet of paper

and places one end to his ear

and one end over the young woman's heaving bosom.

He is delighted by the clarity of the sound.

Laennec spends the next three years developing and testing various materials

and mechanisms

before settling on a hollow wooden tube with detachable plug.

His device becomes the forerunner

to the metal, plastic, and rubber stethoscope we still use today.