The opinion
JOHNSON, Judge
(concurring).
The rule of the Hooker, Rockwell, and Stacy cases applies to “introductory clauses” in claims and provides that such clauses are not to be considered as part of the subject matter of the claim. If there is an introductory clause in claim 93, it must be the portion of the claim preceding the first comma, viz: “The method of measuring high frequency power by means of a bridge circuit having one element variable in resistance in accordance with . excitation thereof, * *
The general rule of those cases that an introductory clause which states only the environment, intended use, or purpose of the stmcture later recited in the claim is not a limitation on the subject matter of the claim is, as the Rockwell case points out, subject to a well defined exception which governs when the introductory clause gives meaning and vitality to the claim. As in Hall v. Shimadzu, 59 F.2d 225 , 19 C.C.P.A., Patents, 1288, 1289, 225, 13 U.S.Pat.Q. 259, the exception to the general rule applies here where the so-called introductory clause is essential to the consideration of the improvement alleged to be inventive and defined by claim 93. While I agree that claim 93 does not define a patentable improvement, I believe that the court’s statement respecting the “introductory part” of claim 93 should not be construed as a precedent extending the rule of the Hooker; Rockwell, and Stacy cases to method claims, such' as claim 93, with introductory clauses which give meaning and vitality to the balance of the claims. See also Kenyon v. Crane, 120 F.2d 380 , 28 C.C.P.A., Patents, 1208; Lawson v. Davis, 129 F.2d 873 , 29 C.C.P.A., Patents, 1217.