You've probably heard the rather crude expression "to heave your guts" used to refer to vomiting. And you probably always thought it was a metaphor -- or at least an exaggeration.
But in the case of some frogs and toads, "heaving your guts" can have a much more literal connotation. A toad that eats something mildly distressing may vomit the object in the same way humans do. But if it has eaten something extremely nasty, such as a poisonous insect, there is a rather more drastic option it may pursue: it can actually throw up its entire stomach. The total-stomach-vomiting mechanism in toads has the same result as emptying a bag by pushing its bottom up through the top: the stomach turns literally inside out and dangles from the toad's mouth. This process is called gastric eversion, and it has been observed in other animals as well as frogs and toads.
Once in the inside-out position, the unwanted contents of the toad's stomach are likely to drop away. To be sure this has occurred, however—and that it isn't about to reswallow the same toxic meal—the toad has a secondary reflex that is associated with stomach vomiting. This reflex causes it to reach up with its front legs and stroke the inverted lining of its stomach several times, thus cleaning it off manually. You could say that this hands-on approach gives new meaning to cleansing the palate.
