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>Physiologus: A Medieval Book of Nature Lore

>XLVI. On the Frog

>There is a frog called the cerseus, meaning "the one from the dry place." This frog is not bothered by the heat during summer but, if he is caught in the rain, he will die. If the water frogs, however, who live in bodies of water look upon the rays of the sun and become warm, they baptize themselves in a stream. "The ones from the dry place" represent fine, abstinent men who are unaffected by working patiently in abstinence; however, if they are caught in the rain (that is, in worldly desires), they die. The water frogs, however, are those who cannot stand abstinence. If these abstain until daytime, not being able to bear a ray of intelligible sunlight, they slip back again into their former desires.