DAVID POGUE (New York Times Technology Columnist): Pythons can eat more than a quarter of their body weight at one sitting. How is the digestive system different from ours?

STEPHEN SECOR (University of Alabama): Most of their digestion is identical to ours. It's just all very long and slender.

DAVID POGUE: A python is basically one long gut, so to see inside, we take one to a nearby veterinarian's office for an x-ray.

Hey, look, snakes welcome!

TECHNICIAN: Ready?

STEPHEN SECOR: Yep, yep.

DAVID POGUE: Wow, you see the rat in there!

STEPHEN SECOR: Ah, it's perfect.

DAVID POGUE: Sure enough, there it is: the python's dinner.

STEPHEN SECOR: The head of the rat is in the pit of the python's stomach, and the stomach extends back, and from this point on, that's esophagus.

DAVID POGUE: Inside the stomach, acids break down the rat, bones, blood and all. Secor x-rayed the python over two weeks. Bit by bit, the rat disappears, and all but the hair is absorbed by the python.

Understanding where the disappearing rat goes can help us understand how our food nourishes us, minus the bones and fur, of course.

To make this point, Secor says, it's useful to compare the rat with a cupcake. After all, to a python, a rat is basically a triple-layer German chocolate cake.

STEPHEN SECOR: Here we have the cupcake and the rat. Both of these have energy stored in them.

DAVID POGUE: Now, even though we don't find these two treats equally appetizing, from the point of view of digestion, what they have in common is that they both are full of potential energy, or calories.

To understand what kind of difference cooking can make to your food, you need to first understand a calorie.

STEPHEN SECOR: Calories represent the amount of fuel that's present with either one of these food items.

DAVID POGUE: Calories are a way of measuring the energy in food, energy your body or a python needs to function.

Think of this cupcake as fuel, like a log on a fire. If we burn it, that fuel will increase the heat of the fire. A calorie is way to represent that increase. Let's burn the cupcake.

STEPHEN SECOR: Okay.

DAVID POGUE: So it is actually burning…

STEPHEN SECOR: Yes.

DAVID POGUE: …like a charcoal briquette or something.

STEPHEN SECOR: Yes, like a, like a log.

DAVID POGUE: Burning the cupcake like this, in the open air, it's impossible to measure the heat it gives off, so Secor shows me the right way to do it, using a machine called a bomb calorimeter.

Items put in the bomb calorimeter must first be dehydrated, since water doesn't burn. Luckily, Secor is prepared for that.

STEPHEN SECOR: This is a dried rat that has been ground up…all the water out of it…kind of mix it all up and then formed a pellet.

DAVID POGUE: All right, well, bring on the bomb calorimeter.

A portion of the dried rat goes into the bomb calorimeter, where it's burned in a special tank, sensitive enough to measure the heat, or calories, in the rat. We do the same thing with our pink cupcake: dehydrate it, grind it up, make a pellet and, as the grad students like to say, "bomb it."

Okay, professor. A nation of eaters awaits the results.

The bomb calorimeter says that seven ounces of cupcake has twice as many calories as seven ounces of rat: impressive and disgusting.

Now, let's take it one step further. Those calories come from the basic elements of eating: proteins, carbohydrates, which are simple sugars, and fats. Secor has calculated the percentage of each in our cupcake and rat.

No matter what we eat, whether it be a cupcake or a rat, those are the things your body is going to extract?

STEPHEN SECOR: That's right, and how they differ and how all meals differ is the relative proportion of each of these elements.

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