The Body: A Guide for Occupants

by Bill Bryson

How many times a day do you suppose you blink? Five hundred? A thousand? You’ve no idea, of course. Well, you blink fourteen thousand times a day – so many that your eyes are shut for twenty-three minutes of every waking day.

Every day, it has been estimated, between one and five of your cells turns cancerous and your immune system captures and kills them.

Don’t forget that your genes come from ancestors who most of the time weren’t even human. Some of them were fish. Lots more were tiny and furry and lived in burrows. These are the beings from whom you have inherited your body plan. You are the product of three billion years of evolutionary tweaks.

We shed skin copiously, almost carelessly: some twenty-five thousand flakes a minute, over a million pieces every hour.2 Run a finger along a dusty shelf and you are in large part clearing a path through fragments of your former self.

We are actually as hairy as our cousins the apes.23

What makes this much worse is that a great deal of our antibiotic use is simply crazy. Almost three-quarters of the forty million antibiotic prescriptions written each year in the United States are for conditions that cannot be cured with antibiotics. According to Jeffrey Linder, professor of medicine at Harvard, antibiotics are prescribed for 70 per cent of acute bronchitis cases even though guidelines explicitly state that they are of no use there.39

Just sitting quietly, doing nothing at all, your brain churns through more information in thirty seconds than the Hubble Space Telescope has processed in thirty years. A morsel of cortex one cubic millimetre in size – about the size of a grain of sand – could hold 2,000 terabytes of information, enough to store all the movies ever made, trailers included, or about 1.2 billion copies of this book.fn1

The nucleus accumbens, a region of the forebrain associated with pleasure, grows to its largest size in one’s teenage years. At the same time, the body produces more dopamine, the neurotransmitter that conveys pleasure, than it ever will again. That is why the sensations you feel as a teenager are more intense than at any other time of life. But it also means that seeking pleasure is an occupational hazard for teenagers. The leading cause of deaths among teenagers is accidents – and the leading cause of accidents is simply being with other teenagers.31 When more than one teenager is in a car, for instance, the risk of an accident multiplies by 400 per cent.

True smiles are brief – between two-thirds of a second and four seconds. That’s why a held smile begins to look menacing.

a genuine, spontaneous smile involves the contraction of the orbicularis oculi muscle in each eye and we have no independent control over those muscles.11 You can make your mouth smile, but you can’t make your eyes sparkle with feigned joy.

The human eye can distinguish somewhere between two million and 7.5 million colours, according to various calculations. Even at the lower end of estimates, that is a lot.

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 afterwards, which is why we are often deafened after an explosion.

MSG has had a hard time of it in the West since 1968 when the New England Journal of Medicine published a letter – not an article or study but simply a letter – from a doctor noting that he sometimes felt vaguely unwell after eating in Chinese restaurants and wondered if it was the MSG added to the food that was responsible. The headline on the letter was ‘Chinese-Restaurant Syndrome’ and from this small beginning it became fixed in many people’s minds that MSG was a kind of toxin. In fact, it isn’t. It appears naturally in lots of foods, like tomatoes, and has never been found to have deleterious effects on anybody when eaten in normal quantities. According to Ole G. Mouritsen and Klavs Styrbæk in their fascinating study, Umami: Unlocking the Secrets of the Fifth Taste, ‘MSG is the food additive that has been subjected to the most thorough scrutiny of all time’, and no scientist has ever found any reason to condemn it, yet its reputation in the West as a source of headaches and low-grade malaise now appears to be undimmed and permanent.

Antibodies, clotting factors and other constituent parts can be separated out and used in concentrated form to treat autoimmune diseases or haemophilia – and that is a huge business. In the United States, plasma sales make up 1.6 per cent of all goods exports, more than America earns from the sale of aeroplanes.34

A teaspoon of human blood contains about 25 billion red blood cells – and each one of those 25 billion contains 250,000 molecules of haemoglobin, the protein to which oxygen willingly clings.

Consider the unfortunate death of George Washington. In December 1799, not long after he had retired as America’s first president, Washington spent a long day on horseback in foul weather inspecting Mount Vernon, his plantation in Virginia. Returning home later than expected, he sat through dinner in damp clothes. That night he developed a sore throat. Soon he had difficulty swallowing and his breathing had become laboured. Three physicians were called in. After a hurried consultation, they opened a vein in his arm and drained eighteen ounces of blood, almost enough to fill a pint glass. Washington’s condition only worsened, however, so his throat was blistered with a poultice of cantharides – what is more commonly known as ‘Spanish fly’ – to draw out bad humours. For good measure he was given an emetic to induce vomiting. When all of this failed to produce any visible benefit, he was bled three times more. Altogether about 40 per cent of his blood was removed over two days. ‘I die hard,’ Washington croaked as his well-meaning doctors relentlessly sapped him. No one knows precisely what Washington’s complaint was, but it may have been no more than a minor throat infection that required a little rest. As it was, the illness and treatment together left him dead. He was sixty-seven years old.

Probably history’s most famous lithotomy, or stone removal, was that experienced by the diarist Samuel Pepys in 1658, when he was twenty-five years old.18 This was two years before Pepys started his diary, so we don’t have a first-hand account of the experience, but he mentioned it frequently and vividly thereafter (including in the diary’s very first entry when he finally started it), and lived in loquacious dread of ever having to undergo anything like it again. It’s not hard to see why. Pepys’s stone was the size of a tennis ball (albeit a seventeenth-century tennis ball, which is slightly smaller than a modern tennis ball, though the distinction could fairly be called academic to anyone carrying one). While four men held Pepys down, the surgeon, Thomas Hollyer, inserted an instrument called an itinerarium up his penis and into the bladder to fix the stone in place. Then he took a scalpel and quickly and deftly – but excruciatingly – cut a three-inch-long incision through the perineum (the area between the scrotum and anus). Peeling back the opening, he gently cut into the exposed and quivering bladder, thrust a pair of duck-billed forceps through the opening, captured the stone and extracted it. The entire procedure from beginning to end took just fifty seconds, but left Pepys bedridden for weeks and traumatized for life.fn1

a mouse’s beats six hundred times a minute – ten times a second. Every day, just to survive, the mouse must eat about 50 per cent of its own body weight. We humans, by contrast, need to consume only about 2 per cent of our body weight to supply our energy requirements.

Even with the advantage of clothing, shelter and boundless ingenuity, humans can manage to live on only about 12 per cent of Earth’s land area and just 4 per cent of the total surface area if you include the seas.

every day you breathe in and out about twenty thousand times, steadily processing some 12,500 litres of air, depending on how big you are and how active. That’s some 7.3 million breaths between birthdays, 550 million or so over the course of a lifetime.

One other enduring myth concerning water intake is the belief that caffeinated drinks are diuretics and make you pee out more than you have taken in. They may not be the most wholesome of options for liquid refreshment, but they do make a net contribution to your personal water balance.

Half of men over sixty and three-quarters over seventy, for instance, have prostate cancer at death without being aware of it.3 It has been suggested, in fact, that if all men lived long enough they would all get prostate cancer.