Try drumming your fingers and watch the skin on your forearm ripple. Or place your hand on the table as if you were doing an impression of a spider with straight legs, tuck your middle finger under your hand and then try to lift each finger in turn. You'll find that you can't lift your ring finger, because the tendons in your fingers are all independent of each other, except for the one controlling the middle and ring fingers, which is shared between the two.

An extreme pedant might point out that there are actually thousands of muscles in each finger, if you count the tiny retractors that cause your hairs to stand up or your blood vessels to contract, but these don't move the fingers.

A commonly repeated factoid is that the tongue is the strongest muscle in the human body. This is plain wrong, not least because the tongue comprises sixteen separate muscles, not one, but even taken together they aren't the strongest, no matter which definition of strength one uses. The strongest muscle is either the largest (here the contenders are the gluteus maximus that makes up most of your b.u.t.tocks or the quadriceps in your thigh) or the one that can exert most pressure on an object (which is your jaw muscle).

However, probably the strongest 'pound for pound' muscle is the uterus: it weighs around 2 pounds (just under a kilogram) but during childbirth can exert a downward force of 400 Newtons, which is one hundred times as strong as gravity and equivalent to the power in a fully extended modern longbow.

Who discovered penicillin?

Sir Alexander Fleming is a long way down the list.

Bedouin tribesmen in North Africa have made a healing ointment from the mould on donkey harnesses for over a thousand years.

In 1897, a young French army doctor called Ernest d.u.c.h.esne rediscovered this by observing how Arab stable boys used the mould from damp saddles to treat saddle sores.

He conducted thorough research identifying the mould as Penicillium glaucu Penicillium glauc.u.m, used it to cure typhoid in guinea pigs and noted its destructive effect on E. coli E. coli bacteria. It was the first clinically tested use of what came to be called penicillin. bacteria. It was the first clinically tested use of what came to be called penicillin.

He sent in the research as his doctoral thesis, urging further study, but the Inst.i.tut Pasteur didn't even acknowledge receipt of his work, perhaps because he was only twenty-three and a completely unknown student.

Army duties intervened and he died in obscurity in 1912 of tuberculosis a disease his own discovery would later help to cure.

d.u.c.h.esne was posthumously honoured in 1949, five years after Sir Alexander Fleming had received his n.o.bel Prize for his re-rediscovery of the antibiotic effect of penicillin.

Fleming coined the word 'penicillin' in 1929. He accidentally noticed the antibiotic properties of a mould which he identified as Penicillium rubrum Penicillium rubrum. In fact, he got the species wrong. It was correctly identified many years later by Charles Thom as Penicillium notatum Penicillium notatum.

The mould was originally named Penicillium Penicillium because, under a microscope, its spore-bearing arms were thought to look like tiny paintbrushes. The Latin for a writer's paintbrush is because, under a microscope, its spore-bearing arms were thought to look like tiny paintbrushes. The Latin for a writer's paintbrush is penicillum penicillum, the same word from which 'pencil' comes. In fact, what the mould cells of Penicillium Penicillium notatum notatum much more closely and spookily resemble is the hand-bones of a human skeleton. There is a picture of it here: much more closely and spookily resemble is the hand-bones of a human skeleton. There is a picture of it here: http://bot.i.t.botany.wisc.edu/Toms_fungi/nov2003.html Stilton, Roquefort, Danish Blue, Gorgonzola, Camembert, Limburger and Brie all contain penicillin.

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Is a virus a germ?

Yes, 'germ' is an informal term for any biological agent that causes illness to its host and so covers both viruses and bacteria.

Viruses and bacteria are quite different. Viruses are microscopic parasites too small to have cells or even their own metabolism. Their growth is entirely dependent on their host. Each infected host cell becomes a factory capable of producing thousands of copies of the invading virus. The common cold, smallpox, AIDS and herpes are viral infections and can be treated by vaccination but not antibiotics.

Bacteria are simple but cellular, the most abundant of all organisms. There are approximately 10,000 species living in or on the human body: a healthy human will be carrying ten times as many bacterial cells as human cells, and they account for about 10 per cent of dry body weight. The vast majority are benign, and many are beneficial. Bacterial illnesses include teta.n.u.s, typhoid fever, pneumonia, syphilis, cholera, food poisoning, leprosy, and tuberculosis and they are treatable with antibiotics.

The word 'germ' comes from the Latin germen germen meaning sprout or bud. It was first used to describe a harmful microorganism in 1871 but it wasn't until 1875 that Robert Koch finally demonstrated that anthrax was caused by a particular species of bacteria. meaning sprout or bud. It was first used to describe a harmful microorganism in 1871 but it wasn't until 1875 that Robert Koch finally demonstrated that anthrax was caused by a particular species of bacteria.

Thirty-five years earlier, Ignaz Semmelweis, a Hungarian doctor had set up the first hygienic hospital ward in Vienna General Hospital. He noticed that the death rate of poor women attended by the nurse midwives was three times less than that of the wealthier women attended by the doctors. He concluded that this was a matter of cleanliness the doctors used to go directly from the morgue to the obstetrics ward without washing their hands. When he presented his findings, his fellow doctors rejected his theory, unable to believe in what they could not see.

In recent years, however, the hygiene itself has come under scrutiny. There seems to be evidence that indiscriminate use of anti-bacterial agents might have damaging side effects, allowing those bacteria that do survive to mutate into even more virulent strains. Also, our immune system, deprived of bacteria and parasites that it has struggled against for thousands of years, has a tendency to overreact leading to a sharp upswing in allergic diseases such asthma, diabetes and rheumatoid arthritis.

Despite this, infectious diseases still kill more people than anything else and 80 per cent of those diseases are transmitted by touch.

Most hygienists recommend that washing our hands regularly with good old-fashioned soap and water is the best and safest way to stay healthy.

What causes stomach ulcers?

It's not stress or spicy food Contrary to decades of medical advice to the contrary, it turns out that stomach and intestinal ulcers are not caused by stress or lifestyle but by bacteria.

Ulcers are still relatively common, afflicting one in ten people. They are painful and potentially lethal. Napoleon and James Joyce both died from complications connected with stomach ulcers.

In the early 1980s, two Australian pathologists, Barry Marshall and Robin Warren, noticed that a previously unidentified bacterium colonised the bottom part of the stomachs of people who suffered from gastritis or ulcers. They cultivated it, gave it a name (Helicobacter pylori), and began to run trials. They found that when the bacteria were eliminated, the ulcers healed.

Even today, most people still think that ulcers are caused by stress. The medical explanation was that stress diverted blood from the stomach, which reduced the production of its protective mucus lining. This gradually left the tissue beneath vulnerable to stomach acid and the result was an ulcer.

What Marshall and Warren were proposing that a common physiological condition, akin to a blister or a bruise, might actually be an infectious disease was unprecedented in modern medicine.

Marshall decided to become his own experiment. He drank a Petri dish full of the bacteria, and soon came down with a severe case of gastritis. He tested himself for the bacteria his stomach was teeming with them and then cured himself with a course of antibiotics. The medical establishment had been proved wrong.

In 2005, Marshall and Warren were rewarded for their tenacity and vision, winning the n.o.bel Prize for Medicine.

Helicobacter pylori is present in half the human population, and in almost everyone in developing countries. It is usually contracted in early childhood and can stay in the stomach for life. It only leads to ulcers in 10 to 15 per cent of those infected. is present in half the human population, and in almost everyone in developing countries. It is usually contracted in early childhood and can stay in the stomach for life. It only leads to ulcers in 10 to 15 per cent of those infected.

We still don't know why this should be, but we do know how to treat it.

JOHNNY VEGAS I refused the treatment, because I preferred to think that I've got sea monkeys living in me stomach. I refused the treatment, because I preferred to think that I've got sea monkeys living in me stomach.

STEPHEN Ah. Yes. Did you get a n.o.bel Prize for that thought? Ah. Yes. Did you get a n.o.bel Prize for that thought?

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What does your appendix do?

Not nothing.

It's not as useless as you've been led to believe.

The appendix is thought to be a remnant from the time when early humans ate gra.s.s. In other primates, such as gorillas and orang utans, the equivalent organ, known as the cec.u.m or caec.u.m (from the Latin for 'blind', as in 'blind alley' or dead end) is much larger and is used to digest the cellulose from the gra.s.s and leaves they eat.

But the human appendix has other more practical uses. Lymphoid tissue (which helps protect the body from bacteria and other foreign invaders) begins to acc.u.mulate in the appendix shortly after you're born and peaks in early adulthood. There is some evidence that the appendix also 'trains' our immune system by producing small amounts of dangerous antigens, which stimulate the production of protective antibodies. More recent research also points to it being a storage centre for helpful bacteria. Given the widespread prevalence of diarrhoea in the developing world (there are an estimated 1.4 billion cases a year), some researchers think its very shape and size make the appendix an ideal reservoir for repopulating the gut with essential bacteria after the disease has flushed the rest of the intestines clean.

The appendix can also act as a backup in reconstructive surgery. It has been shown to be useful if a patient needs reconstruction of the bladder; it can be used as a subst.i.tute sphincter muscle or fashioned into a replacement ureter (the organ that connects the bladder to the kidneys). For all these reasons, it is no longer standard practice for the appendix to be removed during abdominal surgery.

In anatomy, the term 'appendix' can refer to any section at the end of an organ. The correct name for the one we know colloquially as 'the' appendix is the vermiform (or 'wormlike') appendix.

STEPHEN What does your appendix do? What does your appendix do?

JIMMY Does it contain details about me that aren't needed in the main body? Does it contain details about me that aren't needed in the main body?

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What does your appendix do?

Not nothing.

It's not as useless as you've been led to believe.

The appendix is thought to be a remnant from the time when early humans ate gra.s.s. In other primates, such as gorillas and orang utans, the equivalent organ, known as the cec.u.m or caec.u.m (from the Latin for 'blind', as in 'blind alley' or dead end) is much larger and is used to digest the cellulose from the gra.s.s and leaves they eat.

But the human appendix has other more practical uses. Lymphoid tissue (which helps protect the body from bacteria and other foreign invaders) begins to acc.u.mulate in the appendix shortly after you're born and peaks in early adulthood. There is some evidence that the appendix also 'trains' our immune system by producing small amounts of dangerous antigens, which stimulate the production of protective antibodies. More recent research also points to it being a storage centre for helpful bacteria. Given the widespread prevalence of diarrhoea in the developing world (there are an estimated 1.4 billion cases a year), some researchers think its very shape and size make the appendix an ideal reservoir for repopulating the gut with essential bacteria after the disease has flushed the rest of the intestines clean.

The appendix can also act as a backup in reconstructive surgery. It has been shown to be useful if a patient needs reconstruction of the bladder; it can be used as a subst.i.tute sphincter muscle or fashioned into a replacement ureter (the organ that connects the bladder to the kidneys). For all these reasons, it is no longer standard practice for the appendix to be removed during abdominal surgery.

In anatomy, the term 'appendix' can refer to any section at the end of an organ. The correct name for the one we know colloquially as 'the' appendix is the vermiform (or 'wormlike') appendix.

STEPHEN What does your appendix do? What does your appendix do?

JIMMY Does it contain details about me that aren't needed in the main body? Does it contain details about me that aren't needed in the main body?

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What is the worst thing to eat for tooth decay?

Sugar is fine. It's bacteria you need to worry about.

Over 600 species of bacteria live in our mouths. With a single mouth hosting over six billion individual organisms, it isn't surprising that some species (Streptococcus mutans chief among them) cause us problems. By feeding off the sugars in our mouths, they create lactic acid as a by-product. It is this that eats away at our tooth enamel and causes cavities. chief among them) cause us problems. By feeding off the sugars in our mouths, they create lactic acid as a by-product. It is this that eats away at our tooth enamel and causes cavities.

But bacteria don't just eat sugar, they're happy to feed off any kind of starch. The foods that are worst for your teeth are hard-to-shift carbohydrates. Unlike sugars that dissolve quickly in your saliva, cooked starches, particularly potato products such as crisps, cling longer to the teeth, meaning that more acid is produced. Raisins are also particularly good at finding clefts and pits to hide in.

And if that isn't good enough news for the confectionery industry, research from j.a.pan's Osaka University in 2000 discovered that the husks of the cocoa bean contain antibacterial agents that can protect against tooth decay. Enough of these are present in chocolate to make it much less dangerous for your teeth than other high-sugar foods. So next time you're besieged by infants in a till queue, you'll be doing them a favour by loading the trolley with sweets and chocolate and holding back on the crisps and doughnuts.

Dental caries (tooth decay) is the most widespread and common human disease in the world. Ideally, to prevent it, all we need do is brush our teeth after every meal for at least two minutes, to remove all remnants of food from our teeth.

People with gum disease are almost twice as likely to have coronary artery disease than those without. This is because bacteria from the mouth can find their way to the heart, causing blood clots.

According to statistics compiled as part of the 2007 National Smile Week, the UK's dental hygiene is getting worse, not better. 12 per cent of Britons brush only 'a few times a week' or 'never'; fewer than 30 per cent say they brush for two minutes and 60 per cent of people claimed they would happily share their brush with their partner, child, friend or favourite celebrity. Flossing habits turned up a wide variety of utensils, including drill bits, twigs, fish bones, shoelaces and toenails.

Despite this, the number of people having their teeth completely removed has fallen dramatically. In 1968, 36 per cent of the population had false teeth, today fewer than 12 per cent. During the 1940s and 50s, the replacement of all one's teeth with a new set of dentures was a common and popular twenty-first birthday present, particularly for women. They looked regular, stayed brilliantly white and were much easier to maintain.

What are guinea pigs used for?

Lunch.

Guinea pigs, or cavies, are almost never used for vivisection these days, but Peruvians consume an estimated 65 million of them each year. They are also eaten in Colombia, Bolivia and Ecuador. The best bits are the cheeks, apparently.

Ninety-nine per cent of laboratory animals are mice and rats, and more rabbits and chickens are used as 'guinea pigs' than guinea pigs are.

Rats and mice are easier to manipulate genetically and can be made to model a greater range of human conditions than guinea pigs, which were much more popular victims of medical research in the nineteenth century. In 1890, the ant.i.toxin for diphtheria was discovered using guinea pigs and saved the lives of millions of children.

One area where they are still used today is in the study of anaphylactic shock. They are also useful in nutritional research because guinea pigs are the only mammals (apart from primates) that cannot synthesise their own vitamin C and have to absorb it through their food.

Ordinary guinea pigs weigh on average 250 g (about half a pound) to 700 g (around a pound and a half), but researchers at La Molina National University in Peru have developed guinea pigs that weigh a kilogram (or over 2 lb), which they hope will catch on in the export market. The meat is low in fat and cholesterol and tastes like rabbit.

In Peru, the animals are kept in the kitchen because of the ancient Andean belief that they need smoke, and folk doctors in the Andes use guinea pigs to detect illness in people they believe that when the rodent is pressed against a sick person, it will squeak when near the source of disease. In the cathedral of the city of Cuzco, Peru, there's a painting of the Last Supper in which Jesus and the disciples are shown about to eat roast guinea pig.

In 2003, archaeologists in Venezuela discovered the fossilised remains of a huge guinea pig-like creature that lived eight million years ago. Phoberomys pattersoni Phoberomys pattersoni was the size of a cow and weighed 1,400 times more than the average pet guinea pig. was the size of a cow and weighed 1,400 times more than the average pet guinea pig.

n.o.body really knows where the expression 'guinea pig' comes from but the most likely suggestion is that they reached Europe as part of the triangle of slave-trade routes that linked South America to the Guinea coast of West Africa.

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What was the first animal in s.p.a.ce?

The fruit fly.

The tiny astronauts were loaded on to an American V2 rocket along with some corn seeds, and blasted into s.p.a.ce in July 1946. They were used to test the effects of exposure to radiation at high alt.i.tudes.

Fruit flies are a lab favourite. Three-quarters of known human disease genes have a match in the genetic code of fruit flies. They also go to sleep every night, react in a similar way to general anaesthetics and, best of all, reproduce very quickly. You can have a whole new generation in a fortnight.

s.p.a.ce is defined as starting at an alt.i.tude of 100 km (62 miles). After fruit flies, we sent first moss, then monkeys.

The first monkey in s.p.a.ce was Albert II in 1949, reaching 134 km (83 miles). His predecessor, Albert I, had suffocated to death a year earlier, before reaching the 100 km barrier. Unfortunately, Albert II also died, when the parachute on his capsule failed on landing.

It took until 1951 for a monkey to return safely from s.p.a.ce, when Albert VI and his eleven mice companions managed it (although he died two hours later).

Generally, pioneering s.p.a.ce monkeys were not distinguished by their longevity, with the honourable exception of Baker, the squirrel monkey, who survived his 1959 mission by twenty-five years.

The Russians preferred dogs. The first animal in orbit was Laika on Sputnik 2 (1957), who died of heat stress during the flight. At least ten more dogs were launched into s.p.a.ce before the first man, Yuri Gagarin, made it up there in 1961. Six of the dogs survived.

The Russians also sent the first animal into deep s.p.a.ce in 1968. It was a Horsefield's tortoise and it became the first living creature to orbit the moon (as well as the world's fastest tortoise).

Other animals in s.p.a.ce have included chimps (who all survived), guinea pigs, frogs, rats, cats, wasps, beetles, spiders and a very hardy fish called the mummichog. The first j.a.panese animals in s.p.a.ce were ten newts in 1985.

The only survivors of the Columbia s.p.a.ce-shuttle disaster in 2003 were some nematode worms from the shuttle's lab found among the debris.

ALAN If you're a fly, and ... and it's weightless, what happens then? [opens his arms concernedly] Do you suddenly sort of stop flapping and go, 'Hang on ...' If you're a fly, and ... and it's weightless, what happens then? [opens his arms concernedly] Do you suddenly sort of stop flapping and go, 'Hang on ...'

Which has the most neck bones, a mouse or a giraffe?