THE LAST 112 days of his life were not pleasant, but Barney Clark and his family knew the venture upon which they had embarked was risky, and they chose life. When the Seattle dentist died this week after months of hovering between hope and apprehension, millions felt the loss. The world's first recipient of an artificial heart had become an underdog folk hero, a man everyone was rooting for in a cause all wanted to succeed.

Barney Clark was chosen by Utah cardiologists for his role in this experiment in part because of his personal situation. The doctors wanted to work with a patient who had a strong drive to live, a determined will to recover and a cooperative family backing him up. Barney Clark had all the attributes the doctors ordered. He made a tremendous effort to understand and cooperate in the experiment, to bear setbacks with fortitude and to make light of his situation whenever possible. He said last month that if he had lived only a few extra days after the operation the ordeal would have been worthwhile. He hoped that whatever happened to him, others would learn from the procedure.

Others have learned. We know that an artificial heart can work, we know what problems are likely to accompany an implant and we have some idea what the procedure costs. Biomedical experts are already planning smaller, more portable devices, and if experience with pacemakers and artificial hips is any indication, costs will go down as the technology improves and is more commonly used.

In the 112 days after his operation, Dr. Clark lived through another birthday, enjoyed one more Christmas with his family and saw the beginning of a new spring. "All in all," he said, "it's been a pleasure to be able to help people."