In vet school at Cornell, Justin -- a bearded, skinny science-fair type who grew up in the Bronx with pet lizards and snakes instead of puppies -- decided he'd rather be a veterinary sleuth than a veterinary surgeon. "By the time a surgeon gets a patient," he says, "the problem's already known." In his specialty, however, "when you do a probe on an abdomen or heart, you hold your breath a second to see what you find. It can be disturbing. But that's also what keeps it interesting."

Because blood loss is a major issue with surgery on tiny bird parts, St. Marks, with its laser-surgery machine, is the place in the city for avian operations.

Other exotics that visit the clinic include bearded dragons, potbellied pigs, hedgehogs, ferrets, snakes, and hairy chinchillas ("the cutest things in the whole wide world," says the vet). Soon, after renovations, St. Marks hopes to accommodate fish. "If we have to hospitalize fish," she says, "it would be handy to have an aquarium."

Laurie Hess
Board-certified in avian practice
Animal Medical Center
510 East 62nd Street (212-838-8100, ext. 8619; www.amcny.org)

Laurie Hess was just out of Tufts vet school in 1994 when a man burst into the AMC at 3 a.m. with a large, exotic cat and a one-armed baby monkey in a coma. The monkey's seizure had scared the cat into attacking it, and the man wanted Hess to retrieve the simian arm from the feline colon and reattach it. This proved impossible, and the monkey died from what turned out to have caused the seizure: herpes simplex.

"Effectively, someone kissed the monkey, gave it herpes, and killed it," Hess says. Herpes simplex, so common in humans, is fatal to simians.

Since then, Hess and the three other staff doctors in the AMC's exotics department have treated an average of 3,000 animals each year -- not counting emergencies. She recently doctored Izzy, a male guinea pig with breast cancer who made it through a double mastectomy only to contract an unrelated lymphoma. Izzy's owner was willing to do anything to save him, so Hess e-mailed other exotics specialists and oncologists to find a way to give the animal chemotherapy, something the AMC had never done for a guinea pig. Poor Izzy survived one round of chemo but later died.

Cancer in animals seems to be on the rise, says Post, but "it's pretty rewarding to see the progress. The therapies we're using now are similar to those used with people."

Post, who founded the national Animal Cancer Foundation in 1999, disputes the notion that veterinary oncology is grim work. "These are animals who, without intervention, will die. Even if we help, they might still die, but at least we can increase their survival time and quality of life. My patients are happy."

Tim Rocha
Board-certified oncologist
Manhattan Vet Group
240 East 80th Street (212-988-1000)

"A major part of my day is patient education," says Tim Rocha, 34, of his oncology practice on the Upper East Side. The Manhattan Vet Group primarily offers diagnostics and chemotherapy; radiation patients head down to the AMC. Before recommending any course of treatment -- or maybe none at all -- Rocha makes sure the owners understand their options and gives them plenty of time to make a decision.

Since beginning his practice in 1994, Rocha has cared for mostly middle-age to older pets, many with lymphoma or mast-cell tumors. So this is a vet who's sensitive to animals that are likely to have other ailments that might affect their response to chemo or slow the healing process.

About twenty of these gastrointestinal or respiratory cases a week come from veterinary referrals. "A lot of animals are directed here because they need an intervention: They won't eat or have been vomiting and need tube feeding."

Broussard and his team of interns and residents also work on clinical studies, which include testing drugs that are just becoming available for liver and intestinal problems (such as inflammatory bowel disease). "We're like the last step in the stamp-of-approval process," he says.