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You are home to trillions and trillions of tiny living things, and they do you a surprising amount of good.
They provide you with about 10 percent of your calories by breaking down foods that you couldn’t otherwise make use of, and in the process extract beneficial nutriments like vitamins B2 and B12 and folic acid.
lives for no more than twenty minutes—but
But bacteria can swap genes among themselves,
Make no mistake. This is a planet of microbes. We are here at their pleasure. They don’t need us at all. We’d be dead in a day without them.
having hungry microbes may at least partly account for their thinness.)
Viruses are a little weird, not quite living but by no means dead.
They do not propel themselves; they hitchhike.
they are as lifeless as a mote of dust, but put them into a living cell, and they will burst into animate existence and reproduce as furiously as any living thing.
They are also terribly small—much smaller than bacteria and too small to be seen under conventional microscopes.
most viruses infect only bacterial cells and have no effect on us at all.
Something else viruses do is bide their time.
Everyone knows that if you get chilled, you are more likely to catch a cold (that is why we call it a cold, after all), yet science has never been able to prove why—or even, come to that, if that is actually so.
There are, in short, lots of ways to catch a cold, which is why you never develop enough immunity to stop catching them all.
They are actually more closely related to animals than to plants.
where it can grow on the heart and other organs, like mold on fruit.
Altogether fungi are thought to be responsible for about a million deaths globally every year, so hardly inconsequential.
A protist is anything that isn’t obviously plant, animal, or fungus;
The story of Fleming’s accidental discovery of penicillin has been told many times, but hardly any two versions are quite the same.
Every bit of penicillin made since that day is descended from that single random cantaloupe.
Fleming warned that microbes could easily evolve resistance to antibiotics if they were carelessly used. Seldom has a Nobel speech been more prescient.
THE GREAT VIRTUE of penicillin—that
is also its elemental weakness.
What you are left with after a course of antibiotics, after all, are the most resistant microbes. By attacking a broad spectrum of bacteria, you stimulate lots of defensive action. At the same time, you inflict unnecessary collateral damage. Antibiotics are about as nuanced as a hand grenade. They wipe out good microbes as well as bad. Increasing evidence shows that some of the good ones may never recover, to our permanent cost.
The effects, it is feared, may be cumulative, with each generation passing on fewer microorganisms than the one before.
Dismayingly, four of the antibiotics Grant was given didn’t have any effect on the marauding bacteria.
“This was a kid who had been on antibiotics just once in his life, for an ear infection, and yet he had gut bacteria that were resistant to antibiotics. That shouldn’t have happened.”
On some diseases, penicillin now has no effect at all. In consequence, the death rate for infectious diseases has been climbing and is back to the level of about forty years ago.
“We are looking at a possibility where we can’t do hip replacements or other routine procedures because the risk of infection is too high.”
The day when people die once again from the scratch of a rose thorn may not be far away.
THE MOST EXTRAORDINARY thing in the universe is inside your head.
It is, for one thing, 75 to 80 percent water, with the rest split mostly between fat and protein.
The great paradox of the brain is that everything you know about the world is provided to you by an organ that has itself never seen that world.
It has no pain receptors, literally no feelings.
To your brain, the world is just a stream of electrical pulses, lik...
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Your brain is you.
A morsel of cortex one cubic millimeter in size—about the size of a grain of sand—could hold two thousand terabytes of information,
It makes up just 2 percent of our body weight but uses 20 percent of our energy.
Your brain requires only about four hundred calories of energy a day—about the same as you get in a blueberry muffin. Try running your laptop for twenty-four hours on a muffin and see how far you get.
Unlike other parts of the body, the brain burns its four hundred calories at a steady rate no matter what you are doing.
hardest-working brains are usually the least productive.
The main strand of a neuron is called an axon.
The tiny space between nerve cell endings is called a synapse.
At the top, literally and figuratively, is the cerebrum,
It is divided into two hemispheres, each of which is principally concerned with one side of the body, but for reasons unknown the wiring is crossed, so that the right side of the cerebrum controls the left side of the body and vice versa.
Each hemisphere of the cerebrum is further divided into four lobes: frontal, parietal, occipital, and temporal—each
Ironically, as Oliver Sacks once noted, the frontal lobes were the last parts of the brain to be deciphered.
cerebellum
controls balance and complex movements, and that requires an abundance of wiring.
the brain stem.
