This is 99% Invisible. I'm Roman Mars.

Imagine for a moment the year 1800, a doctor is meeting with a patient, most likely in the patient's

home. The patient is complaining about shortness of breath, a cough, a fever.

The doctor listens to the patient's complaints, asks a ton of questions, scribbles some notes,

producer Emmett Fitzgerald, and the doctor might check the patient's pulse, but unlike today,

what's happening inside of the patient is basically unknowable. There's no MRI, no X-rays.

The living body is like a black box that can't be opened. The only way for a doctor to figure out

what's wrong with the patient is to ask them. You needed the patient to tell you what was wrong

and what they were suffering. So doctors were very interested in the patient's history, the story

of what the symptom was, how long it had been there, how it had changed, what made it better,

what made it worse. This is Dr. Jacqueline Duffin. I am a hematologist and a historian of medicine

at Queen's University. Duffin says that because the patient's story was all the doctor had to go on,

the symptoms were often seen as diseases in themselves. So for example, today, if you have a fever,

you think of it as a symptom of some underlying disease like the flu. But back at the turn of the

19th century, the fever itself was considered the disease. There were all different kinds of

fevers, and fever itself was a broad category of diagnosis. Because doctors had no way of connecting

symptoms with what was actually going on inside the body. Until someone built a device that would

help the doctor open the black box and travel inside the human body.

And suddenly the doctor could hear everything so much more clearly. The heart belongs the breath.

And everything changed. The inventor of the stethoscope was unsurprisingly a doctor.

Renee Leineck was born in Brittany in 1781, and he went to medical school in Paris, where he learned

to practice percussion, a technique in which the doctor taps their fingers against a patient's

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