Metaphors are themselves the aptest and clearest mode of expressing much in little. No other form of speech will convey so much thought in so few words. They often compress into a few words what would else require as many sentences. But even such condensations of meaning did not—so it appears—always answer Shakespeare's purpose: he sometimes does hardly more than suggest metaphors, throwing off several of them in quick succession...Here we have a thick-coming series of punning metaphors, all merely suggested. So Brutus, when hunting after reasons for killing Cæsar:
It is the bright day that brings forth the adder.
Here the metaphor suggested is, that the sunshine of kingly power will develop a venomous serpent in the hitherto noble Julius.
From Shakespeare: His Life, Art, and Characters, Volume I. Henry Norman Hudson, New York: Ginn and Co., 1872