Are we really that replaceable?

A fascinating new book explores the science of regenerative medicine... and reveals just how close we are coming to defying ageing and illness

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When science writer Mary Roach lay down inside an iron lung, she hoped to spend a night allowing the mechanical respirator to expand and deflate her lungs - as thousands of polio sufferers did during epidemics in the mid-1900s.

The patient lies inside a big airtight metal cylinder, leaving only their head exposed. The machine then uses negative pressure to control the lungs like a bellows, mimicking natural breathing. It's pretty simple, in theory. But once in position and listening to its chugging motor, Mary discovered the sensation of having a machine breathe for you is an uncomfortable one.

She writes in her new book, Replaceable You: Adventures in Human Anatomy: “You most decidedly are not in charge of your breathing. You will inhale when the machine makes you inhale, and ditto on the exhales. Should you try to defy the machine's rhythm, there will be snorting and mild panic until you fall into line.”

Speaking now from her San Francisco home, the bestselling science writer admits: “I had this idea that I'd spend a night in the iron lung. But it’s an enclosed box - it depends on being a sealed space because you're creating a vacuum to expand the lungs, so it has to be a very tight fit.

CHOKING

“Tt was this weird feeling of, on the one hand, taking deep, luxuriant breaths, and on the other hand feeling like someone is choking you. So it was not really conducive to sleep. I lasted seven or eight minutes! It was fascinating, though not quite what I expected.”