The belief in man's power to change his form and nature is obviously nearly connected with the widespread doctrine of metempsychosis, or the passing of the soul at death into one or a series of animals, generally types of the dead man's character, as where the timid enter the body of a hare, the gluttonous that of a swine or vulture.
"Fills with fresh energy another form, And towers an elephant or glides a worm; Swims as an eagle in the eye of noon, Or wails a screech-owl to the deaf, cold moon, Or haunts the brakes where serpents hiss and glare, Or hums, a glittering insect, in the air."
But while in transmigration the soul returns not to the body which it had left, transformation was only for a time, occurring at stated periods, and effected by the will of the transformed, or by the aid of sorcery or magic, or sometimes imposed by the gods as a punishment for impious defiance and sin.
Other causes, less remote, aided the spread of a belief to which the mind was already inclined. Among these were the hallucinations of men who believed themselves changed into beasts, and who, retreating to caves and forests, issued thence howling and foaming, ravening for blood and slaughter; hallucinations which afflicted not only single persons, as in the case of Nebuchadnezzar, whose milder monomania (he, himself, saying in the famous prize poem:--
"As he ate the unwonted food, 'It may be wholesome, but it is not good'"),
rather resembled that of the daughters of Prætus, who believed themselves cows, but which also spread as virulent epidemic among whole classes. It is related that, in 1600, multitudes were attacked by the disease known as lycanthropy, or wolf-madness (from Greek, _lukos_, a wolf, and _anthropos_, a man), and that they herded and hunted in packs, destroying and eating children, and keeping in their mountain fastnesses a cannibal or devil's sabbath, like the nocturnal meetings of witches and demons known as the Witches' Sabbath. Hundreds of them were executed on their own confession, but some time elapsed before the frightful epidemic, and the panic which it caused, passed away. Besides such delusions, history down to our own time records instances where a morbid innate craving for blood, leading sometimes to cannibalism, has shown itself. Mr. Baring-Gould, in his _Book of Werewolves_, cites a case from Gall of a Dutch priest who had such a desire to kill and to see killed that he became chaplain to a regiment for the sake of witnessing the slaughter in battle. But still more ghastly are the notorious cases of Elizabeth, a Hungarian lady of title, who inveigled girls into her castle and murdered them, that she might bathe her body in human blood to enhance her beauty; and of the Maréchal de Retz who, cursed with the abnormal desire to murder children, allured them with promises of dainties into his kitchen, and killed them, inhaling the odour of their blood with delight, and then burned their bodies in the huge fireplace in the room devoted to these horrors. When the deed was done the Maréchal would lie prostrate with grief, "would toss weeping and praying on a bed, or recite fervent prayers and litanies on his knees, only to rise with irresistible craving to repeat the crime."