delivered the opinion of the Court:
Before proceeding to consider the first question in order, which is the effect of the decision in the first interference, that the appellant contends was a final determination of the matters involved in the second, a preliminary question must be disposed of.
Before an appeal can be taken from an appealable decision of the Commissioner of Patents to the court, notice and reasons of appeal must be filed in the Patent Office within forty days (exclusive of Sundays and legal holidays) from the date of the decision appealed from; and petition for appeal to this court, with a transcript of the record, must be filed within forty days (exclusive of Sundays and legal holidays) from the time of giving the notice of appeal before mentioned. Notice of this appeal was given January 7, 1907, and reasons of appeal filed therewith. The ninth reason is: “That the Assistant Commissioner erred in not awarding priority of invention as to counts 1, 2, 3, and 5 to Horine, and in awarding priority as to such counts to Wende.” On February 1, 1907, notice was served on Wende’s attorney of record, to the effect that under the ninth reason of appeal, aforesaid, appellant would ask a reversal of the decision on the ground that the decision in the former case was conclusive of the matters litigated in this interference. Pursuant to this notice of amendment the same was filed in the Patent Office on February 14, 1907, and made a part of the *422transcript of the record filed in this court February 18, 1907. The petition for appeal filed in this court in accordance with its rules specifically assigns this as one of the questions to be determined on appeal.
Without considering the point whether this court will take notice of a fundamental error, apparent upon the record, that may not have been specially assigned in the reasons of appeal, — which is in the nature of the ordinary assignment of error in actions at law or in equity, — or whether the particular error is embraced within the ninth reason of appeal, as broadly written, we are of the opinion that the amendment of the reasons of appeal should be entertained. Neither the rules of this court nor of the Patent Office mention amendments to the reasons of appeal; but when made, in due time, to correct an assignment that may not be sufficiently specific, or some inadvertence in its preparation, and no possible injury could be done the opposing party,, we see no reason why it should not be permitted. No injury whatever can be done by entertaining the amendment in this case: The rpcord shows that the point was mainly relied on at each hearing in the Patent Office; it is made in the petition for appeal to this court; the opposing party was promptly notified, and admits that he has had ample time to meet the contention. The matter of consideration is one within the exercise of the discretion of this court.
The doctrine of res judicata, or estoppel by former judgment, is thus stated by Mr. Justice Harlan, delivering the opinion of the Supreme Court of the United States: “The general principle announced in numerous cases is that a right, question, or fact distinctly put in issue and directly determined by a court of competent jurisdiction, as a ground of recovery, cannot be disputed in a subsequent suit between the same parties or their privies; and even if the second suit is for a different cause of action, the right, question, or fact once so determined must, as between the same parties or their privies, be taken as conclusively established, so long as the judgment in the first suit remains unmodified. This general rule is demanded by the very objects for which civil courts have been established, which is to secure *423(lie peace and repose of society by the settlement of matters capable of judicial determination. Its enforcement is essential to the maintenance of social order; for the aid of judicial tribunals would not be invoked for the vindication of rights of person and property, if, as between parties and their privies, conclusiveness did not attend the judgments of such tribunals in respect of all matters properly put in issue and actually determined by them.” Southern P. R. Co. v. United States, 168 U. S. 1, 48, 42 L. ed. 355, 376, 18 Sup. Ct. Rep. 18. “The estoppel resulting from the thing adjudged does not depend upon whether there is the same demand in both cases, but exists, even though there be different demands, when the question upon which the recovery of the second demand depends has, under identical circumstances and conditions, been previously concluded by a judgment between the parties or their privies.” New Orleans v. Citizens’ Bank, 167 U. S. 371, 396, 42 L. ed. 202, 210, 17 Sup. Ct. Rep. 905.
In another case upon which the appellee strongly relies in denial of the estoppel in this case it was said: “It must appear, either upon the face of the record or be shown by extrinsic evidence, that the precise question was raised and determined in the former suit. If there be any uncertainty on this head in the record, — as, for example, if it appear that several distinct matters may have been litigated, upon one or more of which the judgment may have passed, without indicating which of them was thus litigated, and upon which the judgment was rendered, —the whole subject-matter of the action will be at large and open to a new contention, unless this uncertainty be removed by extrinsic evidence showing the precise point involved and determined.” Russell v. Place, 94 U. S. 606, 608, 24 L. ed. 214, 215. That was a suit for the infringement of a patent, and the question was the effect of a former judgment recovered by the complainant against the defendant in an action at law for the infringement of the same patent. The answer admitted the recovery of that judgment, but denied that the same issues were involved or determined therein. There was no extrinsic evidence relating to the issues that were determined, and the *424question had to be decided upon the record of the former case. The declaration, in general terms, charged the infringement of the patent by use of the invention of the defendant. The court said: “The patent contains two claims: one for the use of fat liquors generally in the treatment of leather, and the other for a process of treating bark-tanned lamb or sheep skin by means of a compound composed and applied in a particular manner. Whether the infringement for which the verdict and judgment passed consisted in the simple use of fat liquor in the treatment of leather, or in the use of the process specified, does not appear from the record. A recovery for an infringement of one claim of the patent is not of itself conclusive of an infringement of the other claim, and there was no extrinsic evidence offered to remove the uncertainty upon the record: it is left to conjecture what was in fact litigated and determined. The verdict may have been for an infringement of the first claim; it may have been for an infringement of the second; it may have been for an infringement of both. The validity of the patent was not necessarily involved, except with respect to the claim which was the basis of the recovery. A patent may be valid as to a single claim, and not valid as to the others. The record wants, therefore, that certainty which is essential to its operation as an estoppel, and does not conclude the defendants from contesting the infringement or the validity of the patent in this suit.”
The judgment or decree in the former case is not conclusive in the latter one as to matters which might have been decided^ but only to those which were in fact decided. Cromwell v. Sac County 94 U. S. 351, 353, 24 L. ed. 195, 198; Last Chance Min. Co. v. Tyler Min. Co. 157 U. S. 683, 687, 39 L. ed. 859, 861, 15 Sup. Ct. Rep. 733. The issue of the estoppel is that there has been a judicial determination of the fact; and this, includes every fact put in issue and necessary to the judgment, or decree, whether expressly recited therein or not.
To- determine, then, what has been adjudicated in the former1 litigation on which the claim of estoppel is founded, resort is had to the material facts alleged with certainty in the declara*425táon or bill on which the plaintiff’s right to recover is founded; and a general judgment thereon is conclusive of such facts. Hence a final judgment by default or upon demurrer is as efficacious as one rendered after contest between the parties. Last Chance Min. Co. v. Tyler Min. Co. 157 U. S. 683, 690, 691, 39 L. ed. 859, 862, 863, 15 Sup. Ct. Rep. 733. In addition, where there was a contest the finding or opinion of the trial court may, if necessary, be looked to, to render certain that which might otherwise be uncertain. Ibid. See also New Orleans v. Citizens’ Bank, 167 U. S. 371, 402, 42 L. ed. 202, 212, 17 Sup. Ct. Rep. 905. This principle of estoppel by former adjudication is eqxrally applicable to proceedings of a judicial nature in the Patent Office. Blackford v. Wilder, 28 App. D. C. 535, 542.
The difficulty in the application of the principle, that so frequently occurs in ordinary litigation, is often increased by the peculiar character of the proceedings in the Patent Office. The proceedings are ex parte during the process of amendment,, under the suggestions of the Office, leading up to the allowance of the application; and it is only when the interference has been declared and the preliminary statements of the conflicting parties filed, that either has information of the proceedings of the other. The issue of the interference is prepared in the Patent Office. There are no formal pleadings. The applications which contain the descriptions of the invention, and the claims that relate to the matter of the issue, are the foundations of the case. The preliminary statements are required merely to give the respective dates of conception and reduction to practice of the invention described in the application, thereby fixing the boundaries of the evidence relied on for their establishment. To ascertain what facts have been finally adjudicated in an interference, resort must be had to the several applications, the preliminary statements, the claims in issue, the evidence produced, and the decisions of the tribunals of the Patent Office. These decisions, unlike the ordinary judgments of courts of law, are opinions reciting the grounds upon which the award of priority is made, consisting of conclusions in respect of matters both of law and fact.
*426In this case we have before us the entire record of the former-interference, including the applications and claims of the respective parties, their preliminary statements, the evidence and exhibits, as well as the decisions of the several tribunals of the Patent Office which passed on the case in succession. But little additional evidence has been given in the present case, and that wholly on behalf of the appellee. The determination of the second case depended, in the main, upon the evidence introduced in the former case.
The conditions recited are analogous to those presented in the recent case of Blackford v. Wilder, 28 App. D. C. 535, in which it was held that the decision in the first interference between the same parties was conclusive of matters litigated in the second. There are some differences between the two cases, it is true, but they do not materially affect the application of the governing principle. In Blackford v. Wilder somewhat broader claims had been narrowed, pursuant to the requirements of the Office, in order to obtain allowance of patentability at all. After final award of priority to Blackford, by judgment of this court reversing the decision of the Commissioner, Wilder was permitted to amend his claims. His amendment broadened the former claims by omitting a specific feature of the issue of the former interference. This, if finally allowed, would have enabled him to obtain a patent dominating that to which Black-ford had become entitled by reason of the final judgment before rendered in his favor. On the amended claims another interference was declared between him and Blackford. Wilder’s application had been drawn upon a construction called Exhibit E, on which he had chiefly relied in the former interference as evidence of his completion of the invention of the issue therein. He was permitted in the second case to introduce evidence to- show that this exhibit had in it the necessary lighting member when produced in the first case. Of the construction of this exhibit there was no doubt, but the existence of the lighting member was one of the questions expressly decided against him. His amended claims broadened the invention into a claim for a burner omit*427ting the particular lighting member, but in other respects covering the invention described in his and Blackford’s applications. The award of priority in the second case to Wilder was reversed on the ground that the decision in the former case was conclusive of the matter in issue. It was said: “The parties are the same. The applications are the same, and disclose the invention of each issue. The constructions relied on, respectively, as evidencing conception and reduction to practice of the invention of both issues are the same. The fundamental facts of both cases are the same.” Reference was made to the peculiar conditions of practice in the Patent Office permitting amendments after decisions in interference, and to rules thereof, devised to meet, by the application of the principle of estoppel by former decision, as far as possible, conditions that would necessarily call therefor. One of the early decisions of the Commissioner of Patents was also referred to, in which the rule was declared that, while a defeated party might be allowed to make additional patentable claims that could not be made by the prevailing party, none •such should be allowed that could by any latitude of construction be held to embrace matter common to the structures of both parties. 56 Off. Gaz. 141. In Corry & Barker v. Trout v. McDermott, 110 Off. Gaz. 306, it was again said by the Commissioner: “The declaration of a second interference between the same applications should be necessary only in rare cases and under very exceptional circumstances. It should not ordinarily be declared upon claims to the same device and differing from the first issue merely in scope. If a mere change in the •scope of claims were considered good ground for a second interference, the number of successive interferences between the same parties would be practically unlimited, and the interference procedure would become an intolerable burden to applicants. The Office is justified in taking the decision as to priority of invention as prima facie evidence that the successful party was the first inventor, not merely of the particular issue in controversy, but of the invention common to the two cases, whether more broadly or more specifically stated. The burden is upon the defeated party to show special circumstances of the *428particular case which make it improper to apply the decision to the other claims presented. It is not sufficient that the claims differ, and that it is theoretically possible for one party to be the prior inventor as to the first, and the other party prior inventor as to the second, for this would apply in all cases where the claims are not identical.”
It was also said in Blackford v. Wilder, supra, that the principle to be applied is the same declared in the case of two patents issued to the same party, where, to be valid, the second, if it covered matters described in the first, must' be for something essentially distinct and separable from the invention covered by the first. Miller v. Eagle Mfg. Co. 151 U. S. 186, 198, 38 L. ed. 121, 127, 14 Sup. Ct. Rep. 310.
In the case at bar the amended claims were first presented by and patented to Ilorine, and subsequently adopted by Wende; but it is not perceived that this makes any substantial difference between the two cases. The question nevertheless remains: What was determined in the first interference ? It is unfortunate, perhaps, that the Patent Office practice permits amendment by the successful party to broaden the scope of his claims after a final decision in an interference upon claims for the same invention narrower in scope. That question, however, is not before us.
Assuming, for the purposes of this case, without so deciding this time, that Wende would not be precluded, by the decision in the first interference, from making a new claim for a generic invention, separate and distinct from a mere specific form (when not estopped by the conditions stated in Bechman v. Wood, 15 App. D. C. 484, and cases therein cited), we will inquire whether there is such a distinction between his new claims and those involved in the issue of the first interference.
The invention described is of a manifolding copying book, the binged support of which, used in connection with the record book and adapted to fold over so that one or- more copy slips may receive the impression, and be withdrawn for delivery to the buyer and seller, is the essential feature, as shown by its recurrence in the counts of each issue. That Wende considered *429and urged that the counts of the first issue covered his entire invention, as described in his application, appears plainly in the decisions in the former case. His stock-yards’ book represented the improved form of his invention, and, it is said in the decisions in the present case, also embodied all of the counts of the present issue. This, however, was held, in the former case, to have been made subsequently to Horine’s established date of reduction to practice. In addition thereto Wende relied upon said exhibits 1, 2, and 6. In considering them the Commissioner said in his then decision: “It may be admitted that exhibits 1, 2, and 6 and the invention here in issue have certain features in common, and it is possible that those common features are patentable, but the issue contains limitations to features not present in both exhibits.” He then proceeded further to say: “One essential feature of this arrangement (that of the issue) is a support hinged adjacent to the free edges of the adjacent leaves. The support is adapted to be fold upon the primary leaves, and the secondary leaves are secured to it and carry the tertiary leaves. This hinged support is not present in exhibits 1, 2, and 6, and consequently neither the leaves nor the carbon sheets are attached together and arranged in a way called for by the counts of the issue. If by & strained construction of the term it can be said that there is a support for the' secondary leaves, it is not a support having the purpose and function of that in the present devices, and is therefore not the support called for by the issue.”
The hinged support connected with the record book and adapted to fold over for the making and removal of copy slips is clearly the controlling feature of the combination in both issues, and the only reason for holding in the first case that exhibits 1, 2, and 6 did not embody the issue is on the specific ground, as stated by the Examiners-in-Chief in their decision, “that they do not have these secondary and tertiary leaves secured to the hinged support or carried by such support.” It is the omission of these secondary and tertiary leaves that served, in their opinion, to distinguish the one issue from the other.
Wende may have been right in his view that exhibits 1, 2, *430and 6 were sufficient to show conception, at least, of the invention of the first issue, as described in his application, without further broadening his claims- so as to have a like broadening of the issue, in anticipation of technical objections. And the Commissioner may have been in error in his conclusion as regards this point; but whether so or not is not now an open question. Wende, satisfied with his own view, took his chances upon the issue as framed, and, when defeated by the construction given .to the issue and to his said exhibits, failed to appeal from the adverse decision. Whether that decision was right or wrong cannot affect its operation as an estoppel. Having acquiesced in -this decision, in that he failed to take a further appeal, he - might, as above assumed, have made a new claim to a generic invention distinct from a purely specific one, if the former may be so regarded; but he could not, by merely broadening the scope of the former claims to the invention described, bring the subject-matter into litigation again.
In our opinion, these broadened claims do not present the case of a generic invention separable and distinct from the matters covered by the former issue. As admitted in the decision of the Commissioner before quoted, in which he declared that the exhibits did not show a necessary feature of the first issue, they and the invention in issue “have certain features in common.” He declined, however, to give them what ho called “a'strained construction,” that would-bring them within-that issue. As before suggested, he may have been in error in refusing this construction. Be that as it may, however, the most that we are able to say of the amended claims now is that they differ from those of the adjudicated issue in scope merely. We are constrained to hold that this brings them under the rule as applied in Blackford v. Wilder, supra, and the Patent Office and other decisions recited therein with approval.
As this conclusion necessarily disposes of the appeal, there is no occasion to consider any other question in.the case.
Por the reasons given, the decision appealed from will be reversed; and it is so ordered. The clerk will certify this decision to the Commissioner of Patents. Reversed.