Your body produces its own painkillers. They're called endorphins. When you jog 5 miles, or when you suddenly catch your finger in a car door, your brain jumpstarts the factory and dumps crates of Boston Tea endorphins into the bloodstream. These endorphins-- these natural opiates-- pile up in the receptor sites of brain synapses; they relax you, help to float your mind away from the pain you're feeling.

Heroin and Morphine, Codeine and Percocet-- they all contain opiates too. These opiates exactly resemble the body's natural endorphins. Opium-derived opiates will plug into the brain's receptors just as well as natural endorphins.

On a typical day, when you're at work, making photocopies, or walking down to the cafeteria for coffee, your system will cruise the highway at 55 mph. Your body has converted last night's turkey dinner into muscle protein, carbohydrates, amino acids. Now your brain is trickling out a steady flow of low-level endorphins.

But what if you flooded the body with a wash of endorphins? You didn't say a word to the brain, but you piped in a quick burst of opiates.

You'd feel great. You'd feel calm and relaxed.

It would be a freebie. That first time always is. Your brain got distracted. But it kept shouting above the noise, reminded the factory men to keep producing their own steady quota of endorphins.

If you start repeating this unsolicited request-- keep piping-in an extra batch of opiates, every few days or so-- your brain will lose track of its production quota. It will say, "I only need to run the machine at half speed. I think we'll only need to churn out 50% of the daily yield of endorphins."

And you'll feel it the next morning. You'll say, "Why am I so tired?"

But it won't just be the fatigue. The noises of your body will quickly become monotonous and annoying. Your right ankle-- sore from a night of scuffing a black shoe along lower-Manhattan pavement-- will hum with the piercing ache of a TV channel's test pattern siren.

"Damn stop already," you'll scream at the side of your ankle. "Just shut up."

By the end of the day your brain will have panicked, will have called all the men back to the factory.

"Oil the main piston boys, we gotta get up and running."

So, you'll recover. You'll lift back up to calm.

But if, that afternoon, you'd piped in more endorphins from an outside source, you'd have gotten the ankle to shut up.

You wouldn't have felt that great relaxing opiate buzz, though. Sure you'd have felt nice. But no, your body would have diverted half the pipeline, would have sucked it up into dry pores, before you could enjoy it.

Fast forward now. Carry the progress to its full, logical extension. You pipe in a steady stream of daily opiates and your brain closes the entire factory. It sees no reason to compete with the outside pipeline. It stops releasing endorphins entirely.

That's all right though. If you can match the quota, if you can pipe in as many endorphins as your brain used to crank out at the red-brick factory, then you'll live a normal life. Any endorphins piped in above that quota are just a bonus, they'll give you a little of the calm relaxing buzz you felt on day one.

It's all simple math. Remove a gallon from the bottom tap. Pour in a replacement gallon through the top vent. You break even. But make sure you get every last drop of that replacement gallon. Whatever you do, don't be hasty and toss the carton in the recycling bin until you've tapped out those last two drops. There's a digital scale involved here-- it measures volume to the hundredth of a gallon. It will not forgive when you measure out .98.

But why bother with any of this math if you're just gonna break even? Can we get you to pour in an extra pint while you're at it? Can you reward us just a little for the whole exchange?

Of course this is all academic if you can't find a replacement gallon. We may have forgotten to mention this to you but the bottom gallon is gonna get tapped anyway. That tap doesn't shut completely; it'll run out in, say, six hours. Think you can find a replacement gallon by then?

If you can't, then don't concern yourself with your throbbing ankle. Worry more about your screaming skin, the rose thorn pricks of every hair piercing through your forearms, your legs, your ankles.

You can hurry to 1st Street and 1st Avenue. Stand on the corner with a housewife and a Chinese food delivery man. You stand there, hopping from foot to foot, looking in the window of a pricey jazz club. In summertime, the jazz bands will play music for you. But you run around the corner to the stationery store.

"How long?" you ask the kid.

"15 minutes."

A half hour later he's telling a girl on roller blades, "15 minutes." Then she's waiting on the corner too. You're all waiting for the same thing-- pretending you don't know each other.

Finally the fella comes `round the corner. He walks past all of you, never stops moving. You scamper off after him. You're all kids following the schoolteacher across the playground. The teacher hands you a dime and you go back to fill your gallon tank.

You'll always be waiting on that corner. And you'll always be paying good money. Your money will be paying for inflation: the 2 kilos seized by the DEA in December would have hit the street in January. Now January's a little tighter. You're waiting on the corner a little longer. You learn to curse those blaring headlines "Feds crack heroin ring in Chinatown."