Jacob Sprenger, German theologian of the 15th century, and Heinrich Kramer are the authors of the 'Malleus Maleficarum' or 'Witch Hammer’ (1489), which first formulated in detail the doctrine of witchcraft, and formed a textbook of procedure for witch trials. They were appointed inquisitors under the bull 'Summis desiderantes affectibus' of Innocent VIII in 1484, and their work is arranged in three parts — 'Things that pertain to Witchcraft'; 'The Effects of Witchcraft'; and 'The Remedies for Witchcraft.’ It discusses the question of the nature of demons; the causes why they seduce men, and particularly women; transformations into beasts, as wolves and cats; and the various charms and exorcisms to be employed against witches.