Fifteen years later, the magic trick is still fresh in my mind. And magic it is. Not the rabbit-in-the-top-hat, saw-your-assistant-in-half kind of magic, but real-life magic. Teaching magic.
Making an analogy that allows students to see something from their point of view.
|Magic, like most things in life, works best when greasy food is involved.|
In that classroom at UC Berkeley, and in countless classrooms before and since, Dr. Harry Greene used the hamburger trick to help students understand one of the most mind-boggling processes in nature: how a snake with a mouth the diameter of a walnut can ingest a rabbit the size of a football… all with no hands.
|A Western Diamond-backed rattlesnake eats a large rabbit. |
Photo: J. Schofer
The hamburger trick, friends, is the subject of this post.
In contrast, a snake’s skull is a thing of beauty and complexity—by all accounts, an exemplary marriage of structure and function, a marvel of evolution.
|The skull of a Gaboon viper holds the record for fang length— 2 inches!|
|"The last thing I remember, I was looking at a human skull in anatomy class. I must have died of boredom."|
The setup is far more interesting in snakes. The jaw does not attach directly to the rest of the skull, but rather suspends from the skull via the quadrate bone. (You kinda have a quadrate bone, too, but it has migrated, over millions of generations, into your ear—a hear bone.)
So, think of it as snakes having their jaws suspended from the rest of the skull via a mobile quadrate bone. The snake's quadrate bones can basically whirl around on each side. This funky attachment makes the snake’s mouth far more flexible than yours, and also makes the opening larger.
|An egg-eating snake routinely eats eggs several time the diameter of its own head. Notice how the skin stretches between the scale rows. Photo: B. Bouton|
Still not a big enough hole for Peter Rabbit, though. The trick is in the joint at the front of the jaw bone. Your jaw actually consists of two bones (dentary bones) that fuse together at this joint when you’re a fetus. In a snake chin, the dentary bones are connected with a stretchy ligament that allows the two sides of the jaw to stretch away from each other, allowing the mouth to open even larger.
|This image from Digimorph shows nicely how the two dentary bones of the lower jaw are not connected with bone.|
|You can see the two sides of the jaw stretched far apart in this image of a python gorging on a sheep.|
|The articulation of the quadrate bone plus the elastic ligament at the chin allow the burmese python's mouth to open large enough to eat huge prey— like deer, crocs... even humans? lifeslittlemysteries.com|
|Sadie helps show us what a Macrostomatan Harry would look like sucking down a beast-sized burger. Photos: J. Furman|
That’s a big burger. (A mere fraction of the world record burger, weighing in at a ton, but a big burger nonetheless.)
|The record largest burger was made at a Minnesota casino in 2012. It had to be flipped with a crane. But I digress...|
Now you can put it all together and watch Harry doing his magic here:
Abracadabra! That is how the magic is done.