The Grinch's psychological problems have been pretty well analyzed. He has anger and empathy issues, not to mention sociopathic tendencies. No wonder he tried to steal Christmas.
But what about the Grinch's defining physical disability: a heart that was "two sizes too small"?
"It's a tough problem," says Dr. David Kass, a professor of cardiology at Johns Hopkins University who has been studying the Grinch. "We don't see this very much."
There are rare conditions that effectively reduce the size of the heart, Kass says, and they're no fun.
"You're going to have that small heart beating twice as fast" in order to supply enough blood, he says. "That means you're going to feel your heart racing all the time."
That could make you grumpy. And it would definitely make it hard to perform physical labor, like sliding down every chimney in Whoville to make off with all the Christmas presents.
Kass doubts that sort of exertion would even be possible for someone whose cardiac output was so limited. "He would be doing more traditional Grinchy things, just sitting around moping," Kass says.
And from a cardiologist's point of view, the story takes an even more remarkable twist as the Grinch gazes down at the happy Whos from atop Mount Crumpit:
And what happened then...?
Well...in Whoville they say
That the Grinch's small heart
Grew three sizes that day!
That is possible, sort of, Kass says. "There are situations where the human heart can fairly rapidly get large," he says. "But you don't feel good when that happens. This couldn't be Grinch's issue."
So Kass has settled on a different explanation for the Grinch's fast-growing heart: "He's really a snake," he says. "I mean not just any snake, he's a python."
Specifically, a Burmese python.
That makes sense, Kass says, because the heart of a Burmese python is designed to grow rapidly after a big meal.
Like a generous helping of roast beast?
"That would do it," Kass says.
Indeed, Dr. Seuss, author of the 1957 classic book How the Grinch Stole Christmas!, seems to hint at a herpetological explanation in his text. He writes that the Grinch "slithered" around the room where he met little Cindy Lou Who.
But Kass says even the snake-who-had-a-big-meal hypothesis isn't perfect.
"When a snake like a python has done that, does he like run around lifting sleds?" Kass says. "No. He looks like all of us after Thanksgiving. We're on the couch. If we can watch TV, that's about it."
Kass talks about the Grinch's cardiovascular health in this video.
MICHEL MARTIN, HOST:
Let's talk about the Grinch. He's best known for his psychological problems.
(SOUNDBITE OF SONG, "YOU'RE A MEAN ONE, MR. GRINCH")
THURL RAVENSCROFT: (Singing) You're a foul one, Mr. Grinch. You're a nasty-wasty (ph) skunk.
MARTIN: Definitely some anger and empathy issues there, and he did try to steal Christmas. But NPR science correspondent Jon Hamilton wanted to understand the Grinch's physical challenge, a heart that was two sizes too small.
JON HAMILTON, BYLINE: So I went to see a guy who specializes in hearts. His name is David Kass. He's a cardiologist at Johns Hopkins University, and he's been thinking about the Grinch.
DAVID KASS: Tough problem, tough problem 'cause heart at least reputedly is two sizes too small. We in fact don't see this very much.
HAMILTON: Kass says there are conditions that effectively reduce the size of the heart, and they're no fun.
KASS: You're just going to have to have that small heart beating twice as fast. So that means you're going to feel your heart racing all the time.
HAMILTON: Which could make you grumpy. And it would definitely make it hard to do physical labor. So how did the Grinch shimmy up all those chimneys and carry off every Christmas present in Whoville? I ask Kass if that would have even been possible for someone whose cardiac output was so limited.
KASS: No. He would be doing more traditional grinchy things - just sitting around, moping.
HAMILTON: Anyway, from a cardiologist point of view, the story takes an even more remarkable twist.
(SOUNDBITE OF FILM, "HOW THE GRINCH STOLE CHRISTMAS!")
BORIS KARLOFF: (As Narrator) And what happened then? Well, in Whoville they say that the Grinch's small heart grew three sizes that day.
HAMILTON: Kass says this is possible, sort of.
KASS: There are situations where the human heart can fairly rapidly get large.
HAMILTON: Like when a valve suddenly ruptures.
KASS: But you don't feel good when that happens. This couldn't be Grinch's issue.
HAMILTON: So Kass has a different explanation.
KASS: He's really a snake. I mean, not just any snake - he's a python.
HAMILTON: Specifically a Burmese python. That makes sense because the heart of a Burmese python is designed to grow rapidly after a big meal, like, say, a roast beast.
KASS: That would do it. His heart would get large, yeah.
HAMILTON: But Kass says the big meal hypothesis isn't perfect.
KASS: When a snake like a python has done that, does he, like, run around lifting sleds and doing - no. He looks like all of us after Thanksgiving. You know, we're on the couch. If we can watch TV, yeah, that's about it.
HAMILTON: So even a big-hearted Grinch probably would not have returned those toys to every family in Whoville. Jon Hamilton, NPR News.
(SOUNDBITE OF SONG, "WELCOME CHRISTMAS")
UNIDENTIFIED SINGERS: (Singing) Welcome Christmas while we stand heart to heart and hand in hand. Fahoo fores, dahoo dores (ph) - welcome, welcome Christmas - Christmas Day. Transcript provided by NPR, Copyright NPR.