Sam, who is 4 years old, is rushed to Heartland Pediatrics. He is bleeding profusely from a cut on his head. "He fell down the stairs," sobs his mother, Julie. Sam does not seem to be fully conscious and appears confused. Dr. Tony Tyler attends to Sam's laceration, applying direct pressure on the cut to stop the bleeding. He directs clinical assistant Linda Ludemann to call 911 for emergency services. Then Linda takes Sam's pulse. "What are you doing?" Julie asks Linda. What site would Linda use to take Sam's pulse?