Fear such as will constitute extortion, may be induced by a threat, either:
1st. To do an unlawful injury to the person or property of the individual threatened, or to any relative of his or member of his family; or,
2nd. To accuse him, or any relative of his or member of his family, of any crime; or,
3rd. To expose, or impute to him, or them, any deformity or disgrace; or,
4th. To expose any secret affecting him or them.
R.L.1910, § 2683.