The defendant contends that the plaintiffs cannot maintain this action because judgment was rendered for the defendant upon a trial in a previous action between the same parties and for the same cause of action. Evidence was admitted in this action against the defendant’s exception that the former judgment was upon the ground that the first suit was prematurely brought, the goods for the price of which both suits were brought having been sold upon a credit which had not expired when the first action was begun. The judge found as a fact that the only issue decided in the former action was whether that action was prematurely brought, and that the former judgment was entered because the action was prematurely brought and for that reason alone.
The only answer in the former action was a general denial. But under that answer the defence that the goods were bought upon a credit not expired when the suit was begun was open. Wilder v. Colby, 134 Mass. 377, 380, distinguishing Reed v. Scituate, 7 Allen, 141. See also Fels v. Raymond, 134 Mass. 376; Franklin Savings Institution v. Reed, 125 Mass. 365; Benthall v. Hildreth, 2 Gray, 288; Morrison v. Clark, 7 Cush. 213. Whether oral evidence would be admissible to show that a former judgment went solely upon an issue which strictly could not have been tried upon the pleadings as they stood, but was in fact tried with the assent of all parties, is a question upon which we-express no opinion.
*409It is only when rendered upon the merits that a judgment constitutes an absolute bar to a subsequent action for the same cause and the parties are concluded upon all issues which might have been tried. Foye v. Patch, 132 Mass. 105, 110. Tracy v. Merrill, 103 Mass. 280. Maxwell v. Clarke, 139 Mass. 112. Cobb v. Fogg, 166 Mass. 466, 477. In the absence of proof that an issue actually was tried and determined in arriving at a former -judgment, it is conclusive by way of estoppel only as to those facts which necessarily were involved, and without, proof of which it could not have been rendered. Burlen v. Shannon, 99 Mass. 200. Eastman v. Symonds, 108 Mass. 567. See Morse v. Elms, 131 Mass. 151, 152; Watts v. Watts, 160 Mass. 464, 466.
When the question whether a certain issue was in fact determined in a former suit is to be tried, oral evidence is competent upon that question. White v. Chase, 128 Mass. 158. Evans v. Clapp, 123 Mass. 165. Dutton v. Woodman, 9 Cush. 255, 261. McDowell v. Langdon, 3 Gray, 513, 514.
Exceptions overruled.