Well, it's an old legend. You'll find something like it in the folklore of nearly every nation.
5 seconds sound clip from the The Wolf Man (1941) movie soundboard.
You can hear this line at 00:47:23.680 in the Blu-ray version of the movie.
Quote context
[...]
- Richardson was killed last night. The gravedigger.
- The tracks lead up to this house.
- A wolf? Where do you suppose a wolf came from?
- He might have escaped from the circus or a zoo.
- What is this story about a man turning into a wolf?
- Well, it's an old legend. You'll find something like it in the folklore of nearly every nation.
- The scientific name for it is lycanthropia. It's a variety of schizophrenia.
- It's a technical expression for something very simple: The good and evil in every man's soul.
- In this case, evil takes the shape of an animal.
[...]