The Body: A Guide for Occupants

by Bill Bryson

you blink fourteen thousand times a day—so much that your eyes are shut for twenty-three minutes of every waking day.

Altogether it takes 7 billion billion billion (that’s 7,000,000,000,000,000,000,000,000,000, or 7 octillion) atoms to make you.

Your lungs, smoothed out, would cover a tennis court, and the airways within them would stretch nearly from coast to coast. The length of all your blood vessels would take you two and a half times around Earth. The most remarkable part of all is your DNA (or deoxyribonucleic acid). You have a meter of it packed into every cell, and so many cells that if you formed all the DNA in your body into a single strand, it would stretch ten billion miles, to beyond Pluto. Think of it: there is enough of you to leave the solar system.

You would need twenty billion strands of DNA laid side by side to make the width of the finest human hair.

Five out of every six smokers won’t get lung cancer. Most of the people who are prime candidates for heart attacks don’t get heart attacks. Every day, it has been estimated, between one and five of your cells turn cancerous, and your immune system captures and kills them.

We have only thermal sensors to guide us, which is why when you sit down on a wet spot, you can’t generally tell whether it really is wet or just cold.

have the same number of melanocytes. The difference is in the amount of melanin produced.”

When a human body adapts to altered circumstances, the process is known as phenotypic plasticity.

We each grow about twenty-five feet of hair in a lifetime,

Hair grows by one third of a millimeter a day,

The textbook name for fingerprints is dermatoglyphics.

Very, very occasionally, people are born with completely smooth fingertips, a condition known as adermatoglyphia.

Itching (the medical term for the condition is pruritus)

You lose, on average, between fifty and a hundred head hairs every day,

A single parent bacterium could in theory produce a mass of offspring greater than the weight of Earth in less than two days.

The average adult touches his face sixteen times an hour,

Most people in the Western world, by the time they reach adulthood, have received between five and twenty courses of antibiotics.

Even more appallingly, in the United States 80 percent of antibiotics are fed to farm animals, mostly to fatten them. Fruit growers can also use antibiotics to combat bacterial infections in their crops. In consequence, most Americans consume secondhand antibiotics in their food

That is because color isn’t a fixed reality but a perception.

Daniel E. Lieberman observes in The Story of the Human Body,

Colin Grant noted in A Smell of Burning: The Story of Epilepsy,

Anton-Babinski syndrome, for instance, is a condition in which people are blind but refuse to believe it.

Riddoch syndrome, victims cannot see objects unless they are in motion.

Capgras syndrome is a condition in which sufferers become convinced that those clo...

Klüver-Bucy syndrome, the victims develop an urge to eat and fornicate indiscriminately (to the underst...

Cotard delusion, in which the sufferer believes he is dead and cannot b...

Locked-in syndrome is different again. It is being fully alert but paralyzed and often able to communicate only with eye blinks.

Frances Larson notes in her fascinating history of decapitation, Severed,

Broca’s aphasia. (Under it, a person can understand speech but can’t reply except to utter meaningless noises or sometimes stock phrases like “I’ll say” or “Oh, boy.”)

To help protect us from the damage of really loud noises, we have something called an acoustic reflex, in which a muscle jerks the stapes away from the cochlea, essentially breaking the circuit, whenever a brutally intense sound is perceived, and it maintains that posture for some seconds afterward, which is why we are often deafened after an explosion. Unfortunately, the process is not perfect. Like any reflex, it is quick but not instantaneous, and it takes about a third of a second for the muscle to contract, by which point a lot of damage can be done.

When loss of balance is prolonged or severe, the brain doesn’t know quite what to make of it and interprets it as poisoning. That is why loss of balance so generally results in nausea.

We produce very little saliva while we sleep, which is why microbes can proliferate then and give you a foul mouth to wake to.