Kathy Thoreson, age 11, of Mapleton, Iowa, for her question:

How can a snake swallow something bigger than himself?

The mouth of a snake is something special. He has no claws to break his food into small bits and his teeth are not chewers. So if he plans to eat what he catches, he must swallow it down whole. And his special mouth is built to cope with this task, even when his catch is two or three times as wide as his head. The secret is a remarkable lower jaw that can stretch and move in sections.

The lower jawbone is separated in two parts, where the chin should be. The bony division is joined by a section of strong, very stretchable ligament. Two more strips of ligament attach the lower jaw to the upper jaw. When he wants to swallow an oversized bite, he opens up wide, wider and wider. His needle sharp teeth point backwards so that he gets a grip, the food must continue on down his stretchable throat. His two jaws and the two halves of his lower jaw take turns at moving forward to push the food down on its way. Meantime the ligaments and throat stretch wider than wide to make room for it.