The chief of surgery at Children's Hospital National Medical Center said yesterday that the socalled Siamese twin who died at the hospital 11 days ago suffered the larger wound during her separation two months ago from her surviving sister.

Dr. Judson Randolph said Maria, the twin who died of massive infection and blood clotting had the larger opening in her chest. This made it more difficult for her to breathe and necessitated her being kept on a respirator after her sister. Palma, was removed from the mechanical breathing device.

Respirators are common sources of infection in post-surgical and badly injured patients. The tube connecting the machine and the patient provides a pathway into the body for bacteria.

Maria "could not be weaned completely from the respirator." said Randolp. "Her chest wound was a little more severe (than Palma's) and her chest was not stable enough" for her to breathe on her own.

The two girls, born in Italy about five months ago, were more completely joined than any twins ever successfully separated. Unlike most "Siamese" twins, who are connected at the hip, the girls were joined from the tip of the chest to the waist.

They were born with two heads, four arms, two spinal columns and hearts, four lungs two kidneys, one liver and one bladder and set of reproductive organs.

During the 10-hour operation June 23 each girl was left with one leg. Each of the babies was given one kidney, sufficient for survival, one ovary and half a liver.Palma was given the bladder and urinary tract, and an artificial tract was constructed for her sister.

Had both survived, the twins would have had numerous skin grafts to cover chest wounds. The skin would have been removed from other portions of their bodies.

But after Maria died, surgeons removed portions of her skin and grafted it onto Palma. Because identical twins are produced from the division of a single ovum and sperm, their cells and organs are identical. This eliminates any chance of one twin's body rejecting a transplant of tissue - such as skin - from the body of the other twin.

Randolp said additional skin was removed from Maria's body and stored for future use in completing grafts on Palma. However, he said, it is doubtful if the skin can be preserved much longer than it already has been, and will probably never be used.

Maria's death "provided a large impetus tfor the survival of her sister," said Randolph, "because we were not quite ready to take skin from Palma's" own body to cover her wounds.

Randolph said Palma is still suffering from a small opening, or leak, "in the lower part of the intestinal tract, which will probably require surgical closure at a later date."

He said Palma is doing well now, but must still be fed intravenously because of the intestinal problem.

"I think she's going to be a healthy, happy, productive child and adult," he said. The surviving twin will have an "unsightly abdominal scar" and only one leg, "but that in itself isn't something that's going to" cause any major problems.

The child's parents have returned to Italy. Randolph said, but nurses in the hospital's intensive care unit are using some Italian expressions, such as for "good morning" and "good night," around the baby. In addition, he said, the child's mother is sending recordings of her voice.

A hospital spokesman said care of the twins, which has cost more than $100,000 to date, is being absorbed by the hospital, but a fund has been established to help defray the expenses.