Stanton Segal, 79, a physician and researcher who spent half a century trying to cure children with rare metabolic diseases, died of cardiac arrest April 16 at the Hospital of the University of Pennsylvania. Dr. Segal, who worked at Children's Hospital of Philadelphia for 41 years, lived in Merion Station.

Dr. Segal was renowned for research in galactosemia, a metabolic disease in children born without an enzyme necessary for processing milk sugar. He and Gerard Berry - director of the metabolic program at Children's Hospital Boston, who formerly worked at Children's of Philadelphia - also did extensive research on maple syrup urine disease, named because of the sweet smell of the patient's urine. It is relatively common among Mennonites.

Dr. Segal's research showed that if newborns are screened and a metabolic disease is detected early, changing their diet can sometimes prevent brain damage and death.

Many of the metabolic disorders Dr. Segal treated are "orphan diseases - rare, complex, and often neglected by pharmaceutical research," Berry said.

Dr. Segal passionately believed in his work, said Arthur H. Rubenstein, dean of the University of Pennsylvania School of Medicine. "He worked in his lab until shortly before his death."

Dr. Segal was an advocate for the rights of patients in research studies. "He had great respect for patients and incredible humanity," Rubenstein said.

"He always had a smile for us," said Jane Van Zandt of Woodbury Heights, whose son suffers from galactosemia and participated in Dr. Segal's research studies at Children's. "Yet there was an urgency about him. His purpose in life was to study this disease and find a cure."

When confronted with sick babies in the pediatric intensive-care unit, Dr. Segal could "unravel mysterious clinical pictures in a calm and logical manner, while teaching us in the process," said Jack Downes, a physician at Children's. "In metabolic diseases, he was a giant."

Dr. Segal established Children's metabolic diagnostic laboratory in the late 1960s, introducing mass spectrometry and nuclear magnetic resonance.

Born in Camden in 1927, Dr. Segal graduated from Camden High School. When he was 10, he knew he wanted to be a medical researcher, but did not know where he would get the money for school, said his sister, Dorothy Segal. He got scholarships, and earned a bachelor's degree in 1948 from Princeton University and a medical degree in 1952 from Harvard University. After completing training at New York Hospital-Cornell Medical Center and at HUP, he was a senior investigator from 1958 to 1965 for arthritis and metabolic diseases for the National Institutes of Health.

In 1966, Dr. Segal was named senior physician at Children's Hospital and professor of pediatrics at Penn. Soon, he founded Children's division of biochemical development and molecular diseases.

He met his wife, Joan Meth, a student at Wellesley College, when he was at Harvard, and wooed her with poetry and Shakespeare. Dr. Segal recited "Sweet and Twenty" from Twelfth Night on her 20th birthday. They married in 1956.

"He was an ardent gardener," his wife said. "He grew yellow rhododendrons, which are hard to grow. None ever bloomed, until the day he died - when one plant was covered with yellow flowers. That should tell us something about faith, persistence and life."

In addition to his wife and sister, Dr. Segal is survived by sons Mark and Roy and a grandson. Services were private.