Section 3 (4) of the Interstate Commerce Act prohibits carriers from discriminating in their rates between "connecting lines." Appellant Western Pacific Railroad filed a complaint with the Interstate Commerce Commission alleging that certain carriers discriminated against it by refusing to enter into joint through rates via Portland, Oregon, with a multi-railroad route of which Western Pacific is the central portion, although they maintain such joint through rates with a competitor. Division 2 of the Commission refused to accord Western Pacific "connecting line" status on the ground that it did not connect physically with the allegedly discriminating carriers and did not participate in existing through routes with them through the point of discrimination. The Commission denied further hearing and a three-judge federal court dismissed the complaint on the basis that Western Pacific was not a "connecting line." Held:

1. The term "connecting lines" does not require a direct physical connection, but refers to all lines making up a through