An experienced surgeon at Beth Israel Deaconess Medical Center operated on the wrong side of a patient this week, a serious medical mistake disclosed in a memo that hospital administrators sent to staff members today via e-mail. State authorities are investigating the errant surgery, which happened Monday during an elective operation. A hospital administrator declined to provide specifics about the operation but said it did not involve removal of organs and did not cause permanent damage to the patient, described as middle-aged...