Only no one is really sure it will work, because he's a snake, and this was apparently the first time anyone had zapped one with high-energy radiation therapy.
Dogs and cats and people, yes. But it isn't every day that someone strolls through the glass doors of Penn's Matthew J. Ryan Veterinary Hospital carrying a big Rubbermaid container, a 6-1/2-foot South American predator coiled inside.
The story begins in March, when zookeepers noticed a grayish growth on the skin of the anaconda, which the zoo got from an animal dealer in 1981. They didn't know if it was an infection, an abscess, or what.
The vets at Penn took a biopsy, and the news was not good. Squamous-cell carcinoma, right near the animal's vent - an opening through which it excretes waste.
An X-ray showed the tumor had spread to the spine, so surgery was out. There was also an infection because some of the tissue in the tumor was dead: fertile ground for bacteria.
The vets started the snake on antibiotics and cleaned out the tumor. Back at the zoo, he seemed to be doing well, keeping up his 15-pound weight on a diet of dead rats.
The keepers were then told that the anaconda would need radiation to reduce his tumor - for which he'd need to remain motionless. They practiced putting him into a six-foot, flexible plastic tube to hold him still.
At the zoo, in a quiet environment with just two keepers handling him, it worked.
At the hospital Thursday, Sir Mix-A-Lot had other ideas.
The problem was twofold: The environment was chaotic, and his sedative didn't take.
Here's why: A reptile's body temperature fluctuates with its surroundings, and its rate of metabolism and circulation change accordingly.
So unlike with warm-blooded animals, deciding how much sedative to give a snake is a bit of a guessing game, even when a heating pad helps maintain its body temperature.
Half a milligram of medetomidine and 30 milligrams of ketamine worked last time for Sir Mix-A-Lot, when they gave the snake a simple X-ray.
This time, after getting a shot at 9:45 a.m., he remained alert.
When veterinary technician Steve Kobel helped lift the reptile out of its plastic container for the radiation treatment, he got bitten on the hand for his trouble. Thirteen red marks, but not deep. He was more embarrassed than injured.
Then the hard part: getting the snake into the six-foot tube.
You know when you pull the drawstring too far out of a pair of swim trunks, and you have to try to shove it back in?
That's what members of the medical team had to do with Sir Mix-A-Lot and the plastic tube.
Only unlike a drawstring, Sir Mix-A-Lot has muscles.
He tensed up and resisted, and the team members could only slide him in partway.
Finally they decided to go with anesthesia instead, which would mean slipping a tube down the snake's windpipe. For that, the animal would have to open its mouth.
MRI technologist Amy Basatemur went next door to the observation room, and called out: "Does anyone have a blue card?"
She was referring to the plastic hospital identification cards issued to each patient. Someone found Sir Mix-A-Lot's card, and the vets did a neat trick: They gingerly inserted the card between the snake's front teeth, and its mouth popped open.
Vet Nicole Wyre slid in an endotracheal tube and connected it to a supply of anesthesia gas and oxygen.
Though the team had initially hoped the shot would work - because it's easier to administer and less risky - the anesthetic proved a blessing.
Because the snake was out cold, lying perfectly still, Basatemur was able to do an MRI. The scan, shortly after 11 a.m., revealed a key piece of information. Beneath the skin, the tumor was more than two inches across, almost twice the size it was on the surface.
Oncologist Lili Duda knew she had to train the radiation over a larger area. The big machine went on, and the snake got a 2-1/2-minute dose.
Then the team, led by Karen Rosenthal - chief of the hospital's "special species" section - slowly woke up the patient.
He'll be back for five more weekly treatments. Then the doctors can see if the tumor is shrinking.
Sir Mix-A-Lot is at least 30 years old and likely would live just five more years even without the tumor.
"We don't truly expect a cure," Duda said. "We hope to control it long enough so it's not cancer he dies of."
Contact staff writer Tom Avril at 215-854-2430 or email@example.com.