After 40 years it has become a tired truism that anyone old enough to remember the assassination of President John F. Kennedy can remember clearly where they were and what they were doing when they first heard the news from Dallas.

For Dr. Robert G. Grossman, this classic "flashbulb" memory is not just a vivid personal recollection. It is one of acute professional and historical significance.

On Nov. 22, 1963, Grossman was a 30-year-old neurosurgeon in Dallas. He had been on the staff at Parkland Hospital for just five months when a telephone call — which he and his colleagues at first suspected was a particularly bad joke — summoned them to Parkland's Trauma Room 1. Kennedy, they were told, had been shot.

In the decades since, Grossman has rarely spoken about what he saw in that room. He never wrote down his recollections. And to his surprise, the Warren Commission, which investigated the assassination, never called him to add his testimony to that of others who were there.

Grossman is 70 now, and chairman of neurosurgery at Baylor College of Medicine in Houston. In the interest of history and medicine, he has finally shared his recollections as part of a series of articles in the journal Neurosurgery exploring the "neuroforensics" of the Kennedy assassination.

The articles were co-written with Daniel Sullivan and Rodrick Faccio, both of the Keck School of Medicine at the University of Southern California; and Dr. Michael L. Levy, of Children's Hospital in San Diego. The first part, published this month, includes Grossman's memories of the events; the next two parts will correlate the trauma-room account with autopsy reports, eyewitness accounts and ballistic evidence.

"The goal of this series of reports," the authors say, "is to establish a reasonable hypothesis regarding the pathological mechanisms that killed President Kennedy."

Grossman, father of three and grandfather of eight, conceded in a recent telephone interview with The Baltimore Sun, that memory "is a very tricky thing.'

Henow regrets his failure to record his observations at the time. "I was just too shocked," he says. "Many of the people who were there wanted to put it behind them. It was a horrible experience, and I didn't think I could really add anything."

He is nevertheless confident about his recollections. "I think something like that is so dramatic that the things you remember, you remember accurately," he says.

As Grossman and fellow neurosurgeon Kemp Clark, then 38, made their way to Parkland's trauma center, across a parking lot from their laboratory at the Southwestern Medical School, the confusion of police cars and limousines at the ambulance dock told them this was no prank. Their walk became a sprint.

When they entered the room, Kennedy was making some "gasping breaths," Grossman says. The room was already crowded with doctors. One had performed a tracheotomy, inserting a breathing tube through an opening in Kennedy's neck that incorporated a small bullet hole — the exit wound from the first shot, which struck Kennedy in the upper back, according to the Warren Commission.

"Mrs. Kennedy was standing against the wall, on the left side of the president, toward his feet," Grossman says in Neurosurgery. "Her face was very white and she appeared to have been crying. She was wearing a light-colored dress. The lap of her dress was covered with blood and brain tissue."

Grossman and Clark made the first examination of Kennedy's head wounds. "You could see he had a head wound, but I don't think anyone really understood its dimensions," he told The Sun. "So Dr. Clark and I went to the head of the table and picked his head up."

"He had very thick, brushy hair," Grossman recalls. Parting it, "you could see the bone was blasted outwards by a bullet coming out." In fact, the right side of the president's skull, just above the ear, opened upward like a hinged door, 4 inches wide and 2 inches high.

The hole was filled with badly damaged brain tissue. "I think it was obvious to everyone who saw the wound that this was not a recoverable wound," Grossman says. "He might have lived for two hours or two days. But he certainly would never have recovered."

Lifting Kennedy's head higher, Grossman and Clark saw a small wound about an inch in diameter on the upper part of the back of his head, just to the right of the midline. It, too, was filled with damaged brain tissue.

"My conclusion was that he had been shot in the back of the head, and the bullet blasted out the right posterior parietal area."

Grossman had seen a number of head wounds caused by handguns during his time at Parkland but never one caused by a bullet with this kind of power.

"It was clearly not a pistol," he says. "This was such a huge injury, it clearly had to be a bullet traveling at a much higher velocity. I don't think you could tell what angle it was shot at, but it was definitely from the rear and definitely a rifle."

The other physicians in the room, meanwhile, were struggling to keep Kennedy alive. They could feel no pulse, and the electrocardiogram showed no organized electrical activity in his heart.

"Closed cardiac massage was used to attempt to maintain circulation and to start the president's heart," Grossman wrote in Neurosurgery. Resuscitation efforts continued for about 15 minutes, but "it became apparent to us that the president's heart could not be restarted.

"Dr. Clark went to Mrs. Kennedy, who was standing in the room, and comforted her as best he could. Dr. Clark, who was the senior surgeon present, pronounced President Kennedy dead at approximately 1 p.m."

Only about 12 minutes had elapsed since Grossman and Clark had entered the trauma room.

"I think people (in the room) were very upset," Grossman says. "But nobody was crying. Nobody was out of control. I don't think it was chaotic at all."

Most of those in the room went into the corridor while nurses prepared Kennedy's body and placed it in a casket. The mood was one of shock and fear.

"I think everyone was concerned that this was the start of World War III," Grossman says. "We had just been through the Cuban missile crisis, a nuclear standoff, and I think everyone was thinking, 'What better way to start World War III but to kill the president and strike the country with missiles?' "

After the Secret Service took Kennedy's casket away, he says, "most people went home to take care of their families. I did, because I had two small children at that time, and I was sort of concerned about them."

Grossman had one more brush with history. Two days after Kennedy's death, he was called in to examine Lee Harvey Oswald, the man suspected in the president's assassination, for signs of a spinal cord injury. Oswald had been shot by nightclub owner Jack Ruby while in police custody. He found no spinal damage, but Oswald died soon afterward in the operating room.

Until the project for Neurosurgery, Grossman had never read the Warren Commission report, nor any of the myriad books about the assassination, nor the conspiracy theories it spawned.

He has read some of that material in the past year, however, and says nothing he saw that day seriously conflicts with the commission's conclusions.

Even with 40 years of historical perspective, he rejects the notion that he was somehow privileged to participate in the events of Nov. 22, 1963. "It was just something that happened," he says. "You try to do as good a job as you can with it. Then you go on. I certainly didn't do anything which was heroic."

By sharing his recollections now, he only hopes to contribute his piece to the medical record of the assassination, and perhaps to encourage others to do the same.

"There are still many things we don't understand," he says. "Perhaps eventually more information will come to light, and we will have a clearer picture."