QI: The Second Book of General Ignorance

by John Lloyd

  It’s their smooth, curved shells that helped them survive for so long. They’re hard for predators to overturn and expose the soft underside, though Native Americans once used them as bailers to scoop water out of their canoes.

  As well as their extraordinary blood – now known to be able to detect meningitis and cancer as well – horseshoe crabs can endure extremes of heat and cold and go for a year without eating.

  They also have ten eyes. Which is odd, because Polyphemus, the giant of Greek mythology they’re named after, only had one.

  STEPHEN It’s the blood of the horseshoe crab.

  JACK DEE When you get given it, do you walk out sideways?

  What’s the best way to treat a jellyfish sting?

  Don’t urinate on it!

  There’s a well-established urban myth that urinating on a jellyfish sting relieves the pain. In fact, it doesn’t – and could make it worse.

  The sting of a jellyfish comes from specialised cells in the skin of its tentacles called cnidocytes (literally ‘nettle-jars’, from Greek cnide, ‘stinging nettle’, and cytos, a ‘vase’ or ‘vessel’).

  Each small, bulb-shaped capsule holds a coiled, barbed, thread-like tube, filled with poison and sealed in under high pressure. On the outside of each cell is a tiny hair called a cnidocil (Latin cilia for eyelashes). Touching this ‘hair-trigger’ explodes the cell’s minuscule toxic harpoon into your skin in 700 billionths of a second.

  It is the fastest known mechanism in nature.

  Feeling or scratching a jellyfish sting is not a good idea. It sets off any other unfired sting cells clinging to the skin, and you get stung on your hand as well.

  Brush off any loose tentacles with a towel and splash the sting with salt water to wash away any unfired cells. Fresh water is no good: the change in the salt content of the water also activates the cells and injects more venom.

  There’s a lot of fresh water in urine – you can survive by drinking it if you have to – and, depending on who’s doing the urinating, a lot of other stuff as well. It may contain harmful bacteria that can infect the wound. (Don’t be fooled by the ‘fact’ that human urine is sterile. It is when it leaves the bladder, but it has to pass through the urethra which contains plenty of germs, all of them waiting to multiply in a warm, hitherto unoccupied medium like urine.)

  Many Australian beaches have supplies of vinegar (5 per cent acetic acid) available in case of jellyfish stings. This can work – if you know the species you’ve been stung by. But some jellyfish have acid stings and some have alkaline ones. Vinegar is a good temporary remedy for the deadly Australian box jellyfish, but only exacerbates the sting of the Portuguese man of war.

  Pain is not necessarily the worst thing about jellyfish stings. They can cause anaphylactic shock. Watch out for swelling, itching, rashes or shortness of breath. If you spot any of these symptoms, don’t waste valuable time urinating on the patient – call a doctor.

  What causes pins and needles?

  Ordinary pins and needles have nothing to do with poor circulation.

  They happen when pressure on a part of the body compresses the nerve cells and impedes the blood flow. When the pressure is released and the blood flow returns to normal, numbness gives way to tingling as oxygen and glucose are restored to the nerves. This can affect anywhere on the body – though it’s usually found in arms, legs, hands or feet – and passes within a few minutes. The technical term for it is ‘transient paraesthesia’, Greek for ‘altered feeling’.

  If you suffer from chronic pins and needles, however, you might want to get a professional opinion. It can be symptomatic of a stroke, brain tumour, brain abscess, multiple sclerosis, rheumatoid arthritis, HIV, Lyme disease, cancer, alcoholism, malnutrition, exposure to radiation or whiplash injury.

  Disturbing though that list is, it won’t lead to the onset of belonephobia, the ‘fear of pins and needles’. That only applies to fear of sharp points (belone is Greek for ‘needle’). There is no such word as paraesthesiaphobia – at least, there wasn’t until just now.

  The indescribably peculiar feeling you get when you bang your ‘funny bone’ is a close relative of transient paraesthesia. The ‘funny bone’ isn’t a bone – it’s the ulnar nerve, which is unusually near the surface. The twinge comes from it getting jammed up against an actual bone, the humerus, which starts at the shoulder and ends at the elbow. Banging it produces dysaesthesia, meaning an unpleasant sensation, as opposed to paraesthesia, which is merely an unusual one.

  A good way to get pins and needles is to sit on one of your feet, a pose that was very popular in nineteenth-century Turkey. In the travel book Constantinople in 1828 by Charles Macfarlane, the author noted that the polite sitting position for ladies in Smyrna was ‘with one leg on the sofa bent under them, and the other hanging over the edge’. This led a visiting Frenchman to ask whether ‘this unipedal exhibition’ meant that ‘all the women in the city had but the one leg’.

  In the USA 27 November is official Pins and Needles Day, though few people know why. It commemorates the opening night, in 1937, of a unique Broadway musical. Pins and Needles was produced by the International Ladies’ Garment Workers’ Union, and the cast was made up of union members. Despite being ignored by mainstream theatre critics, the show ran for 1,108 performances, a record only overtaken by Oklahoma! in 1945.

  Finally, in case you’re wondering, acupuncturists do claim to be able to treat pins and needles. They may not ask you how you got them: paraesthesia is one of the side effects associated with acupuncture.

  What causes a hernia?

  It’s not the strain of lifting something heavy.

  Hernia is Latin for ‘rupture’ and is the condition in which a bodily organ (or part of one) breaks through into a part of the body it shouldn’t be in. This could be the brain protruding through a defect in the skull, or a loop of intestine escaping from the abdominal cavity and ending up in the chest.

  The most common use of the word hernia refers to tissue that has protruded through the abdomen. Heavy lifting never causes this – although straining the abdominal muscles by lifting something heavy might make an existing, unnoticed hernia more prominent.

  A hernia is caused by a lack of collagen (the protein in skin and muscle tissue that makes it flexible) in the affected area. This can be the result of genetic abnormalities, of smoking (which breaks down the collagen in your body) or just the general wear-and-tear of advancing age. Only one in ten people who are diagnosed with a hernia will have discovered it by straining themselves.

  The most common type of hernia in the UK is the inguinal hernia (from Latin inguen, ‘groin’), in which a segment of bowel slips down into the scrotum, using the same route as the descending testes during puberty. If it gets caught, and cannot return easily, it can ‘strangulate’ – causing violent vomiting and abdominal pain and requiring immediate surgery.

  But this misfortune is a weakness that you are born with: it’s not caused by strenuous exercise.

  Why should you avoid the free peanuts in bars?

  You’ll have heard about the scientists who tested a bowl of peanuts in a bar and found traces of urine belonging to twenty-seven different people. Johnny Depp certainly has; he mentioned it during an appearance on The Tonight Show with Jay Leno in July 2005.

  This alarming tale is trotted out again and again, and it’s in the back of many people’s minds every time they reach for the bar snacks.

  As far as we know, there has never been any such scientific study but, in 2003, the London Evening Standard conducted an informal tour of six London bars and took away samples of the free snacks. Tests showed that four of the six contained enterobacteria, which are also found in faeces.

  There is certainly cause for concern about many people’s attitudes to toilet hygiene. In 2000 the American Society for Microbiology asked a thousand people whether or not they washed their hands when visiting a public lavatory and 95 per cent said they always did. The Society’s researchers
weren’t convinced and so they set up hidden cameras to see how people actually behaved. The percentage of those who really did wash their hands turned out to be 58 per cent.

  Another US survey produced the even odder statistic that 8 per cent of Americans are so frightened of catching germs from lavatories that they flush with their feet.

  The French, at least, are more honest – or perhaps less paranoid: 56 per cent of men and 66 per cent of women admitted to researchers that they never wash their hands after visiting les toilettes. This prompted a French engineer to develop a device that locked users inside restaurant lavatories until they’d done so.

  The peanut factoid is sometimes told about bowls of complimentary mints in restaurants, with exactly the same wording. When the news of this reached Canada and was reported in the Ottawa Sentinel in 1994, the regional health authorities sent out their inspectors to ensure that all such mints were either ready-wrapped, or were offered in such a way that they could ‘only be handled by one person at a time’.

  Which is riskier: nuts or mints? The answer turns out to be ice cubes.

  Recent official studies of both hotels and pubs in Cardiff and fast-food joints and bars in Chicago found that at least 20 per cent of all ice cubes were contaminated with ‘faecal matter’ caused by staff failing to wash their hands.

  In January 2010 a study at Hollins University in Roanoke, Virginia reported that almost half the drinks from ninety local soda fountains tested positive for coliform bacteria, indicating possible faecal contamination.

  On a more optimistic note, they also noted that there were no reported outbreaks of food-related illness in Roanoke at the time of the study.

  But please, now wash your hands. And don’t shake anyone else’s.

  What is household dust made from?

  The composition of house dust has been extensively studied because of its role in allergies. Not much of it is dead skin.

  It’s quite difficult to get meaningful data because dust varies so widely from country to country, house to house, and even room to room. It also depends on the season and on the lifestyle of the householder – whether you have a pet, how often you clean, whether you open the windows etc.

  What is clear is that the allegation that house dust is 70 per cent human skin is wildly exaggerated. More common sources of dust include flakes of animal skin, sand, insect waste, flour (in the kitchen) and lots and lots of ordinary dirt.

  The dead skin we shed each year would be enough to fill a small flour bag, but most of it is drained away in bathwater or eaten by dust mites.

  Dust mites are tiny, fat, eight-legged members of the spider family. They live in beehives and in birds’ nests as well as in human homes. Half a teaspoon of dust may contain as many as 1,000 mites and 250,000 droppings.

  They also live in beds, but the idea that dead dust mites and their waste products make up half the weight of your mattress or pillow is nonsense.

  Bedding manufacturers (particularly in the USA) are in no hurry to discourage these rumours.

  Most people who react badly to dust are actually allergic to dust mite faeces. Enzymes excreted from the mite’s gut attack the respiratory passages, causing hay-fever-like symptoms or asthma.

  Such allergies aside, there’s no reason to worry about mites: you’re already supporting a thriving community of them on your face.

  Follicle mites (Demodex follicularum) live exclusively on human beings. They are long (about a hundredth of an inch) and slim (to fit snugly into the follicles). They have microscopic claws and needle-shaped mouthparts, which they use to pierce skin cells. They can’t walk backwards, so once they’ve burrowed head first into somewhere comfortable like the base of your eyelashes, they’re stuck for life. They eventually dissolve away harmlessly in situ, rear end last.

  This rear end is an interesting sight: unlike dust mites, follicle mites create so little waste that they don’t even need an anus.

  STEPHEN Now, what is house dust mostly composed of?

  VIC REEVES Rust.

  STEPHEN ‘Rust’! I don’t think mostly of rust, no.

  VIC If you live in an iron house like me …

  What might land on your head if you live under a flight path?

  A huge block of frozen urine? It has never happened and it never will.

  Aeroplanes do not dump the contents of their lavatories overboard. The waste is contained in a holding tank, which is emptied when the aircraft lands. Great care is taken to ensure that this tank is secure. Even if a mad pilot wanted to jettison it, access to the tank is located on the outside of the plane.

  On very rare occasions, ice can fall from aeroplanes. Some 3 million flights pass through British airspace every year; in the same period, the Civil Aviation Authority gets just twenty to thirty reports of possible icefalls. The CAA investigates all such complaints by checking the relevant flight paths. Over the past twenty years, they estimate that five people have been hit by small amounts of falling ice.

  In July 2009 a lump of ice the size of a football crushed the roof of a car in Loughborough, Leicestershire, but no flights were in the area at the time and the incident has been put down to a freak conglomeration of hailstones.

  If ice does fall from a plane, it is either water that has frozen on the wings owing to the high altitude (which melts off as the plane comes into land) or water from the air-conditioning system that has leaked through a faulty seal on to the fuselage. Aircraft toilets often add a blue chemical to the water to deodorise the waste and break down any solids, but any blue ice that falls to the ground is a result of a fault in the input pipe. It cannot come out of the toilet itself or from the holding tank, which is a fully integrated, sealed unit.

  In the USA the Federal Aviation Authority is equally adamant. No American has ever been hit by anything falling from an aircraft lavatory. Phone calls to the FAA complaining about brown droplets coming from the sky always increase during the bird migration season. The FAA also blames so-called ‘blue ice’ on incontinent birds that have been eating blueberries.

  Like planes, modern trains in the UK carry chemical retention tanks, but some older rolling stock still offloads its toilet waste straight on to the tracks.

  Around Britain’s coastline, there are 20,000 pipes pumping untreated sewage into the sea. These ‘combined sewer overflows’, or CSOs, are intended as a last resort when there is a danger of an urban sewage system flooding. But heavy rainfall in recent summers means that some have been in almost constant use. As a result, in 2009, almost half of Britain’s beaches were ‘not recommended’ for swimming by the Marine Conservation Society’s Good Beach Guide.

  Resorts that failed to come up to scratch included fashionable destinations such as Rock in Cornwall, Sandgate in Kent and West Sands in St Andrews. It was the worst result for Britain’s beaches for eight years and bad enough for the European Commission to decide to take the UK to court to try to get CSO discharges banned.

  ALAN Urine. Frozen urine. It kills you and you just look like you’ve pissed yourself. To death.

  What are your chances of surviving a plane crash?

  They’re very good indeed: especially if you’re in the cheap seats.

  In the USA, between 1983 and 2000, there were 568 plane crashes. In 90 per cent of them there were survivors and, out of a total of 53,487 people onboard, 51,207 survived. According to Popular Mechanics magazine the safest place to be in the event of a crash is at the back, well behind the wings, where there is a 69 per cent survival rate. Sitting over (or just in front of) the wing reduces your chances of getting out alive to 56 per cent. The worst place to be is right up at the front in first class, where the survival rate falls to 49 per cent. Which is an outrage, considering how much you have to pay to sit there.

  According to the world’s leading ‘fire safety engineer’, Professor Ed Galea of the University of Greenwich, the biggest danger is seatbelts. In an emergency, passengers panic and revert to what they are familiar with: they struggle to open the
m like a seatbelt in a car, resulting in (sometimes fatal) delay. Fire is, of course, a major problem, largely because of smoke inhalation. Your safest bet is to sit on the aisle close to an exit. Before take-off, make a note of how many rows there are between you and the nearest door. That way, even if the cabin is filled with smoke, you’ll still be able to crawl your way out by feel.

  Until recently, it was thought impossible for a passenger airliner to make a successful emergency landing on water. The margin for error is so small. To prevent the plane breaking up on impact, the pilot must slow down as much as possible – but without losing lift – and raise the nose of the plane to 12 degrees so that the tail hits the water first. The wings must be perfectly level: if one wing-tip hits the water before the other the plane will cartwheel and break up. The fuel must be used up or dumped: its weight would cause the plane to sink even if it did land successfully. Then there’s the weather, and sea conditions, either of which could wreck the plane, no matter how calmly the pilot behaves.

  Despite such unnerving obstacles, there have been at least half a dozen successful emergency landings by airliners on water, including one off the coast of Sicily in 2005. The most recent and spectacular example occurred in January 2009 when an Airbus A380, US Airways Flight 1549, ditched in the Hudson River in New York. Shortly after take off, the plane hit a flock of geese and Captain Chesley ‘Sully’ Sullenberger III had to make a forced landing on the water. He did this perfectly, saving the lives of all 155 people on board.