With so much foreign material passing by, a warm, moist tongue ought to be a luxuriously rich nesting site for bacteria. Why is it, then, that tongues rarely get infected and heal rapidly after injuries? Molecular biologist Michael Zasloff, president of Magainin Research Institute, thinks he knows. Last March, Zasloff and his colleagues detected a microbe-killing peptide on cow tongues. Zasloff inspected cow tongues bearing slight wounds from grazing and found, sure enough, that wherever tissue was injured, the cells on the surface of the tongue were making more peptides. But the importance of Zasloff’s find goes far beyond the tongue. He found that the peptide is produced on every other wet surface of the cow’s body--the eyes, the lining of the gut, the airway. And he has already identified similar antibiotic peptides in the gut and airway of humans--as well as in the skin of a frog and the stomach of a shark. The amazing thing, he says, is that in some places, like the tongue, which are exposed to a continual assault, you always have a low level of expression, so there’s a barrier all the time. But when you’re injured, the barrier doesn’t get weak--it gets stronger.