DIFFERENT BLOODLINES -- Nurse Hathaway (Julianna Margulies) makes a surprising discovery when animal activists are brought into the ER after a car accident. Dr. Corday (Alex Kingston) looks for candidates to help with her study on artificial blood and then deals with unexpected complications in her relationship with Dr. Benton (Eriq La Salle). Jeanie (Gloria Reuben) and Scott Anspaugh (guest star Trevor Morgan) hear bad news regarding his illness. Dr. Greene (Anthony Edwards) learns that Dr. Ross (George Clooney) has come to a decision regarding his future at the hospital. Dr. Morgenstern (William H. Macy) returns to the ER for the first time since his heart attack, causing mixed emotions in Dr. Weaver (Laura Innes). Dr. Del Amico (Maria Bello) contends with a distraught husband while trying to help his wife avoid a miscarriage. Dr. Carter (Noah Wyle) continues to watch over his cousin, Chase (guest star Jonathan Scarfe). TV-PG