R. T., in his Blazon of Jealousy, tells a story of a swan near Windsor which, finding a strange male with his mate, swam I know not how many miles after him to kill him. Having done so, he returned and killed his own female. This is a certain truth, he says, something that happened on the Thames, as many boatmen and local gentlemen can testify. “Let him make good his word.” For my part, I believe it may be true, for swans have always been branded with the epithet “jealous.”

The jealous swan that sings as his death approaches, And also the owl that brings the omen of death.

Some say the same of elephants: that they are more jealous than any other creatures whatever. And the ancient Egyptians, as Pierius informs us, represent the passion of jealousy in their hieroglyphs by a camel, “because, always fearing the worst in sexual matters, he loves solitude so that he may enjoy his pleasure alone”; “and, goaded by jealousy, he attacks anyone he encounters.” In his jealous fits he will quarrel and fight with whoever comes near, human or animal.

I have read the same of crocodiles; and if Peter Martyr’s testimony is trustworthy, you will find a strange tale confidently told to this effect in book 3 of his Babylonian Embassy. For another story, about jealousy in dogs, see Girolamo Fabrici’s On the Speech of Animals, treatise 3, chapter 5.

But this furious passion is most conspicuous in human beings, among bachelors as well as married men. When it appears among bachelors, we commonly call them rivals or fellow rivals, a metaphor derived from a stream: “rivals from rivus, a stream.” Just as a stream, say Acron in his commentary on Horace’s Art of Poetry and Donatus on Terence’s Eunuch, divides land held in common between two men, and both share in it, so a woman stands impartially between two suitors, each with a prospect of possessing her. From this comes the rivalry that often breaks into tempestuous storms and produces lamentable effects: murder itself, much cruelty, and many duels.

They cannot endure the slightest injury done to them in front of their mistress, and in her defence will bite off one another’s noses. They are utterly intolerant of any mockery, disgrace, or the least rivalry or sharing of this kind.

“Biting Memmius mangles Largus’s arm.” The Roman Memmius, as Cicero tells the story in On the Orator, book 2, was Largus’s rival at Terracina and bit him on the arm. This deed became so famous that it afterwards passed into a proverb in those parts.

Phaedria could not endure his rival Thraso. When Parmeno asked, “Do you have any further orders?”—whether he wanted any other service from him—he said, “Nothing more, except to speak on his behalf and drive away his rival if he could.”

Constantine, in book 11, chapter 11 of his work on farming, tells a delightful story about the pine tree: “She was once a beautiful maiden, whom two rivals, Pineus and Boreas, eagerly courted; but jealous Boreas broke her neck,” and so on. In chapter 18 he tells another story, of Mars, who killed Adonis in his jealousy.

Petronius calls this passion “the furious rivalry of lovers”: a furious rivalry. Their symptoms are well expressed by Sir Geoffrey Chaucer in his first Canterbury tale.

It will make the closest and dearest friends quarrel. They will tolerate the sharing of everything else—goods, lands, money—share one another’s pleasures, and take any other kind of insult or injury in good part. But, as Propertius aptly describes it in one of his elegies, in this matter they will yield nothing and admit no rivals.

Destroy my heart with steel or poison, Only keep away from my mistress. You may share my life and my body; I grant you mastery of my possessions, my friend. Only my bed, that one bed, I beg you to leave alone: I cannot endure even Jupiter as a rival.

Stab me with a sword, or give me strong poison To bring about my death, Provided you do not court my girl, provided you Keep away from my mistress. Command me, my body and my purse; Take everything as your own property, And as my dearest friend I shall always treat you. Oh, leave my love alone; I long To have her to myself. No, I will not endure even Jove himself As my rival.

The jealousy I am to discuss is that of married men concerning their own wives. Just as no sweetness, pleasure or happiness in the world can compare with their condition if they live peacefully and lovingly together, so, if they quarrel or become jealous, those bitter pills of sorrow and grief—disastrous harms, misfortunes, torments, agonies and discontents—cannot be separated from them.

Where it takes hold, it is an extremely violent passion, an unspeakable torment, a hellish torture, an infernal plague, as Ariosto calls it: “a fury, a continual fever, full of suspicion, fear and sorrow, a martyrdom, a monster that destroys joy.”

“The sorrow and grief of heart of one woman jealous of another is heavier than death,” Ecclesiasticus 28:6; as Peninnah did to Hannah, “tormenting her and bitterly reproaching her.”

It is a great affliction, an utterly intolerable burden, something that eats away all contentment, a frenzy, madness itself, as Benedetto Varchi demonstrates from that choice sonnet by Giovanni della Casa, that reverend lord, as he styles him.