the merits constitutes an absolute bar to a subsequent suit upon the same cause of action in respect to every matter offered and received in evidence, or which might have been offered to sustain or defeat the claim in controversy, while if the second suit is upon a different cause of action the judgment in the prior action operates by way of estoppel (herein called res judicata) only as to those matters in issue or points controverted upon the determination of which the finding or verdict was rendered. Southern Pacific Railroad Company v. United States, 168 U. S. 1, 50 (1897). This distinction was followed in Southern Pacific Railroad Company v. United States, 183 U. S. 519, 533 (1902); Radford v. Myers, 231 U. S. 725, 730 (1914); Oklahoma v. Texas, 256 U. S. 70, 77 (1920); United Shoe Machinery Corporation v. United States, 258 U. S. 451, 458 (1922). Myers v. International Trust Co., 26 U. S. 64, 70 (1923).

The same distinction in a trade mark proceeding. The difference between these two rules is well illustrated by a trade mark case, in which it was held that when the question of similarity of trade marks has been settled in a proceeding for a "technical trade mark", the applicant's right to a ten-year trade mark is not thereby barred by judgment, but the question of similarity of marks is res judicata. Barclay v. Carter, 41 App. D. C. 240; 198 O. G. 238; 1914 C. D. 97. It will be seen that the question of similarity of marks was not merely potentially present, but was actually determined.

"On the merits." "Privies." "Same cause." Consideration will first be given to the rule of bar by judgment, and to the terms used in the statement of that rule, that is to say: "judgment on the merits," "the same parties or their privies," "the same cause of action."

Judgment on the merits. A judgment on the merits does not necessarily mean a judicial determination designated by the name "judgment." Any determination, which is based on the merits and has the effect of finally determining the rights of the parties is sufficient. A motion to dissolve may or may not result in a determination

of the merits. When a motion to dissolve, on the ground that a party has no right to make the claim because his alleged invention is inoperative, or because of two years' public use, is granted, there has been a determination on the merits. On the other hand if a motion to dissolve has been granted because of a defect in the disclosure of the application, or because of irregularity in declaring the interference, it would seem that there has been no determination on the merits. A second interference was refused, when the first had been dissolved on the ground that the party could not make the claim. U. S. ex rel Newcomb v. Moore, 30 App. D. C. 464; 133 O. G. 1680; 1908 C. D. 332. The Newcomb opinion does not state the reason that the party could not make the claim in the first interference. When, however, the motion to dissolve is granted for the purpose of correcting a defect in a party's drawing, there is no bar. Moore v. U. S. ex rel Colburn, 40 App. D. C. 201; 191 O. G. 293; 1913 C. D. 398. If a party in interference is required to file an affidavit under rule 75, but instead of doing that puts his claims into an earlier application, and has an interference set up on this earlier application there has been no adjudication on the merits. Rotter v. Hodgkinson, 43 App. D. C. 254; 213 O. G. 1118; 1915 C. D. 103.

Same parties or privies. The same parties or their privies include common assignees of different inventors claiming the same invention. Temple & Goodrum, 176 O. G. 526; 1912 C. D. 70. McKenzie v. Garrett, 43 App. D. C. 6; 212 O. G. 1689; 1915 C. D. 83. If the common assignee owns the invention during the interference, the rule applies even tho one of the applications is not filed until after testimony has been taken in the interference. Frickey v. Ogden, 199 O. G. 307; 1914 C. D. 19. When, however, the common assignee had been demanding an interference on the other application, the dissolution of the first interference was held not to determine his rights. Campbell v. Dyson v. Dunham, 242 O. G. 253; 1917 C. D. 56.

The more difficult question of persons who were not strictly in privity with the inventor, but who were, nevertheless, substantially represented in the first proceeding, sems not to have arisen as yet in interference proceedings. A judgment against joint inventors not based on the fact that the application was joint, is a bar to one of the joint applicants, on a sole application. Miller v. Lambert, 72 O. G. 1903; 1895 C. D. 77. The Commissioner of Patents may set up on an ex parte proceeding, the rights that might have been set up by the party with whom the present applicant was formerly involved in interference. Henderson, 50 App. D. C. 191; 269 Fed. 707; 284 O. G. 182; 1921 C. D. 133, 135. In at least one reported case it was held that res judicata, (evidently meaning what is herein called bar by judgment) was applicable to a situation in which. the first interference included a party who could not have made the proposed new count. Robinson v. Copeland, 187 O. G. 514; 1913 C. D. 39, affirmed, 39 App. D. C. 504; 188 O. G. 1055; 1913 C. D. 332. Laches or estoppel might be applicable, under some circumstances, to such a situation. But to say that a thing which not only was not adjudicated but which could not have been adjudicated is res judicata (thing adjudicated) is stretching the term beyond all meaning. The case seems to be overruled, by necessary implication, in In re Martin, 48 App. D. C. 187; 257 O. G. 408; 1918 C. D. 213.

Same cause of action. The term most difficult to define, is "the same cause of action". Owing probably to the failure to distinguish between bar by judgment and res judicata there has been some confusion as to what constitutes the same cause of action in the Patent Office. The rule of res judicata applies even tho the causes of action are different, therefore it is not necessary to find that the causes of action are the same in order to apply this rule. But the rule of bar by judgment is applicable only when the causes of action are the same. The test for what constitutes a different cause of action which is about to be stated will not be immediately acceptable to all minds. Furthermore it departs from, altho it is not

necessarily inconsistent with, language sometimes used in opinions. Cutler, 48 App. D. C. 444; 261 O. G. 801; 1919 C. D. 191, 193. If properly applied, however, it should not lead to any undesirable results.

A cause of action generally is "matter for which an action may be brought". Bouvier's Law Dictionary, Third Revision, 1914, vol. 1, p. 436. The definitions of the term are legion, and many of them have been collected, but that which has been given will suffice. Words and Phrases, Second Series, 1914, vol. 1, pp. 599-604.

In patent interference practice a cause of action is a claim to a monopoly sufficiently different from other claims to sustain a separate patent. Even tho an applicant discloses only a single species he may have to contest an interference on a broad claim with one applicant, and a narrow claim with another. Each of these interference would usually be based on patentably distinct claims, and therefore based on a separate cause of action. Difference in scope is enough to make the cause of action different, if the difference in scope is sufficient so that it would sustain a separate patent upon a differ ent disclosure. This view as to what constitutes a separate cause of action finds support in a Supreme Court case, in which it was held that a judgment which might have been rendered on either of the claims of a patent, but failed to disclose clearly upon which it was rendered, did not fix, as between parties, their rights with respect to one claim, because the prior determination might have been made on the other claim. In other words a suit on one claim is a different cause of action from a suit on another claim of the same patent. Russell v. Place, 94

U. S. 606 (1876).

It follows that applicants are never barred by judgment from contesting with each other a second interference having a count or counts patentably different m scope from the counts of an interference which they have already contested. As we shall see presently the loser in the first interference may be doomed to defeat in the second interference, by reason of the rule of res judicata.

But this is a matter of evidence to be presented in the second interference. As far as the rule of bar by judgment goes, there may be a series of interferences between the same parties, over the same general subject matter.

Public policy. Such a series of interferences should be avoided if possible, from the point of view of the of fice, of applicants, and of the public. The rule of res judicata will limit abuse to some extent. Diligence by the office in suggesting claims of different scope may help somewhat. If these two safeguards are not sufficient it may be necessary to use the doctrine of laches, which has already proved a valuable weapon in forcing applicants to assert their rights promptly. It is this doctrine which ordinarily limits patentees to two years for applying for broadened reissue, and limits applicants to a similar period for copying claims from patents. Webster v. Splitdorf, 44 Sup. Ct. 342 (1924). The possibility of utilizing the doctrine of laches for preventing a multiplicity of interferences will be somewhat explored after res judicata, estoppel, and other equitable doctrines have been discussed.

Res judicata elaborated. The rule of bar by judgment is sufficient in itself, if successfully set up, to determine the rights of the parties. The rule of res judicata, however, is merely in the nature of a rule of evidence, which conclusively establishes one or more facts upon which the rights of the parties depend. The judgment must usually be specially pleaded if it is relied upon as a bar in ordinary court procedure, but it may be proved under the general issue if relied upon merely to establish that one or more facts are res judicata. 23 Cyc. 1523.

Therefore when a patent applicant attempts to prosecute a claim which he has lost in interference he may properly be rejected on the ground that his right to this claim has been adversely decided. The same would be true for any other claim not patentably different in scope. Votey, 114 O. G. 259; 1905 C. D. 1. Nelson v. Felsing, etc., 32 App. D. C. 420; 142 O. G. 289; 1909 C. D. 358. Reid, Reid & Kelly v. Kitselman, 275 O. G. 624; 1920