At 3:40, the atmosphere abruptly changed. The hospital's station at Logan Airport called to report that there had been an accident: a dozen construction workers had been injured and were on their way in police cars and ambulances. At least two of the injured were going to Boston City Hospital; as many as ten might come to the MGH. The extent of injuries was not known, but some might be very severe.

The emergency-ward administrator put out a disaster call, notifying the chiefs of all departments of the impending emergency and its nature. The chiefs in turn arranged for mobilization of all available hospital personnel from other wards. In a matter of minutes, interns, residents, and senior men began to appear in the EW. The nurses and staff were already clearing patients out of the treatment rooms; the corridors were cleared and supply carts checked. Privately, everyone agreed that it was fortunate the day had been a slow one, for there was practically no back-up.

Emergency-ward personnel are always concerned about back-up. The emergency ward is geared to treat a new patient every eight minutes, around the clock; the staff is prepared to admit to the hospital one out of every five of these emergency patients, or a new admission every forty minutes. This is a furious pace, but it is standard procedure for the hospital. And although patient flow through the EW is generally smooth, there is almost always a back-up. At any time-and this day was an exception-the emergency ward may have three to ten people in the lobby waiting to be seen; another six to ten in the various treatment rooms; another four or five in the back room waiting for X rays, orthopedic examinations, or sutures of minor lacerations. This is the back-up, and the residents keep an eye on it; when it begins to swell, everyone worries, because there is no way to predict when there will be a six-car automobile crash, or a fire, or some other disaster that will strain the hospital's facilities for emergency care.