Released in 1941, The Wolf Man came to be known as the film that revived Universal horror. The Wolf Man is one of the few monster films where the source material isn't based on literature; it was also instrumental in contributing to the mythology and legend of the werewolf. The idea that a werewolf could be killed by silver, that a person would become a werewolf through a bite and change during a full moon all came from this film. Perhaps the most significant item to have come from this film is the oft repeated poem "even a man who is pure in heart may become a wolf when the wolfbane blooms and the autumn moon is bright." Some people truly believe this to be gypsy folklore, but it was actually writer Kurt Siodmak who created it, along with the other werewolf "folklore". While this may not have been the first werewolf film, Werewolf of London has that honor, it is the most significant in contributing to the mythology for all werewolf films to follow.