No fixed rules of interpretation determine whether a guarantee is a continuing one or not, but each case must be judged on its individual merits. Frequently, in order to achieve a correct construction, it becomes necessary to examine the surrounding circumstances, which often reveal what was the subject matter which the parties contemplated when the guarantee was given, and what was the scope and object of the transaction between them. Most continuing guarantees are either ordinary business securities for advances made or goods supplied to the principal debtor or else bonds for the good behavior of persons in public or private offices or employment. With regard to the latter class of continuing guarantees, the surety's liability is, generally speaking, revoked by any change in the constitution of the persons to or for whom the guarantee is given