Felix Frankfurter,
City of Indianapolis v. Chase National Bank of New York…
“ Jurisdiction of the federal courts is indeed a variable and illusory thing, if the jurisdiction which a District Court admittedly has of two separate causes of action is lost when they are united in one, agreeably to the federal rules of procedure, because the one defendant as a surety seeks to enforce its equitable right to be exonerated by the other who is alleged to be the principal debtor. ”
