Secor, who grew up on a horse farm, planned to be a veterinarian, but a love of snakes derailed him. At first, he tried to study their behavior in the lab (the mating habits of the speckled king snake), but he found the research boring. So for his Ph.D. at the University of California, Los Angeles, Secor headed out into the field to track a pair of wild species — the coachwhip and the sidewinder rattlesnake — and learn how they managed their metabolism in a natural setting. As eaters, these snakes were polar opposites. Secor noticed that the coachwhip, whose form is long and slender, was always on the move, chasing little lizards through the Kelso Dunes. A sidewinder waits for its dinner: It sits in ambush until a kangaroo rat happens to come hopping by, and then it has a banquet.

When Secor presented his observations at a 1991 scientific meeting at White Mountain Research Center, a few hours north of Los Angeles, Jared Diamond raised his hand. Diamond, now better known for his work as a geographer and historian (he is the author of “Guns, Germs and Steel”), was at the time a physiologist in the mold of Francis Gano Benedict. Since the early 1980s, he had been working on a grand survey of animal digestion. His lab had looked at rats and mice, cats and minks, frogs and fish. He had even studied how a hummingbird handles so much nectar in its small intestine.

Diamond thought of the intestine as something like a muscle, lifting substances into the bloodstream. If you had to do more lifting, he reasoned, you would need to have a stronger muscle. So Secor’s talk about the sidewinders, and their feast-or-famine diet, made him wonder if the animals’ intestines were endowed with superhero strength. As it happens, Secor had tried to measure the rattlesnakes’ metabolism, but the numbers he got were so high that they seemed impossible. A mammal’s metabolic rate typically rises by one-quarter or one-half after feeding. The largest such increase anyone had ever measured in a reptile was a fourfold or fivefold change. But Secor’s data showed that sidewinders could increase their metabolism by almost eightfold — a bigger jump than anyone had seen in any species. A prominent scientist at U.C.L.A., who would later serve as Secor’s mentor, told him that he must be doing something wrong. “Leave the physiology to physiologists,” the professor said.

But when Diamond looked at Secor’s numbers, he believed them. “This is the most exciting data I’ve seen in five years,” he announced. As soon as Secor finished his dissertation, he moved his work to Diamond’s lab. It soon became apparent that, as research animals, Secor’s three dozen wild rattlesnakes were not ideal. “Every now and again, he’d get bitten, and then he’d get a little dizzy,” Diamond remembers. Secor says the venom didn’t bother him much, but U.C.L.A.’s administration was not keen on housing a colony of sidewinders. So Secor and Diamond set out to find a safer snake with an athlete’s intestine. Secor tested a Noah’s ark of options — a pair of water snakes, a pair of corn snakes, a pair of black racers, a pair of Burmese pythons — before he found his champion. The python’s gut looked even more impressive than the rattlesnake’s. After feeding, the intestine blew up like a bodybuilder’s, doubling in mass.

And if the python’s meal was very large, its metabolic rate would increase not just eightfold, like the rattlesnake’s, but by a factor of 44. The only comparable metabolic increase Diamond knew of had been identified in a galloping racehorse. The most impressive short-term increase he had seen in humans — measured in water-polo players and cyclists in the Tour de France — was no more than five or six times their resting rate. “These pythons made the Tour de France cyclists and water-polo players look like wimps,” he says. What’s more, the python could sustain that level of metabolism for several days.

Secor kept a pair of 12-footers in his home, Linus and Bob; he knew pythons were easy to acquire and maintain. The pet trade in the Burmese python had been booming since the 1980s. So he reached out to a guy he knew in Oklahoma, who happened to be the nation’s biggest python breeder, and put in an order for 100 snakes. Over the next few years, Secor worked on tracing how a Burmese python’s body transforms itself after feeding. Nearly every facet of digestion was exaggerated, he found, from the way the python fills its stomach with hydrochloric acid to the way its organs thicken and expand. For him and Diamond, the scale of these effects had a scientific value of its own. It made the process of digestion easier to study, because every nuance could be seen in high relief.

But as Secor finished this initial round of work, Diamond was preparing to move on. “The future of the world does not depend on intestines and gallbladders,” he had decided. In the fall of 1998, he and Secor summarized their research on pythons in the journal Nature. Their article was half-prospectus and half-plea — a call to fellow physiologists to make the Burmese python a standard laboratory animal. The snakes were practical, the article said, on account of their infrequent feeding and inexpensive upkeep, their convenient “linear anatomy,” their easygoing nature and their relative lack of moral standing. (Snakes “do not arouse the controversy associated with medical research on similarly sized mammals,” Secor and Diamond noted.) But the Burmese python’s greatest value — its raison d’être as a laboratory species — derives from its special way of eating.