It's a technical expression for something very simple: The good and evil in every man's soul.
6 seconds sound clip from the The Wolf Man (1941) movie soundboard.
You can hear this line at 00:47:35.400 in the Blu-ray version of the movie.
Quote context
[...]
- 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.
- What's the matter with you, Larry?
- But do you believe in these yarns?
[...]