SOUTH OF KARBALA, Iraq — Four soldiers from the 2nd brigade of the 101st Airborne Division, with red sores on their faces and hands, were sent by ambulance to a rear MASH unit Tuesday. They were told they would be examined for possible contact with nerve or blistering agents. Once at the 30th medical brigade's mobile hospital at the 101st's headquarters south of Karbala, the soldiers were isolated from other troops and photographed. A doctor at the MASH, Maj. David Wolken, interviewed each soldier and measured his pulse and heart rate in a tent with a dirt floor. One soldier...