Former Medical School professor Clarence Dennis, who performed the world’s first open-heart surgery that used a heart-lung machine, died July 11. He was 96 years old.

“(Dennis) recognized the need for surgeons to stop having blood go through the heart while they operate,” said David Rothenberger, University professor of surgery and interim chairman of the department of surgery.

“He recognized that they were going to have to have some temporary way to keep the person alive,” he said.

In 1947, Dennis was a professor of surgery at the University but left in 1951 for a job in Brooklyn, New York.

Known by his colleagues, family and friends as an inventive and curious person, he continued to contribute to his field even after his retirement.

When he retired, he returned to Minnesota to work with the University’s Cancer Detection Center.

“He came back here because this is his home,” said Dr. John Najarian, a University professor of surgery.

Dr. William Sullivan, who knew Dennis as a family friend and colleague for more than 15 years, noted that Clarence Walton Lillehei, who is considered “the father of open-heart surgery,” was Dennis’ student.

“This is really one of those cases where we stand on the shoulders of those who came before us,” he said.

Dennis’ “single greatest contribution” was his work on the heart-lung machine, Sullivan said.

Dennis had macular degeneration, a disease that causes blindness in aging people. Despite this condition, his interest in education wasn’t slowed. He invented a machine that he would wear while attending conferences. It consisted of a hood attached to a screen two inches from his eyes, which magnified what was in front of him.

“There he would be, in the very front row, enclosed in this hood with a screen in front of his eyes, and he would still participate, ask questions and make good comments,” Rothenberger said.