Before Nevin Katz decided to become a physician, he thought about being a rabbi.

He was interested in people, but he was also interested in science, which is what finally decided him on medicine.

At 38, after four years of college (Swarthmore, '67), four years of medical school (Case-Western Reserve, '71) and nine more years of training (Massachusetts General, Children's Hospital in Boston and the University of Alabama Medical Center in Birmingham), his career is just beginning to accelerate. He shows none of the flamboyance or arrogance so often associated with surgeons. If anything, he seems somewhat shy. When he comes to operate, he gives the impression that he is taking a test for which he has spent months preparing.

He has an earnest, solicitous bedside manner coupled with seemingly bottomless good nature that Frances Leatherman found assuring. In the operating room, Nevin Katz is all heart--no talk of stocks, tax shelters or hot sports cars (he drives a 1980 Chevrolet Malibu and his wife has a 1975 Malibu).

He also appears to be unflappable. "I guess one of the reasons why surgery training is as long as it is," he says, "is not only to learn many disciplines that will help you in your own discipline, but to train one never to be upset with the situation to the extent that it affects how you treat it. Sometimes things are not the way you would want them to be . . . When a situation gets bad, I think the only way one can look at it is to say, 'This is a very challenging situation' and one just has to draw on every resource possible to correct it."

If someone makes a mistake, or if the operation takes a turn for the worse, then, Katz says, "You just have to say, 'Now it's more of a challenge . . .' And I think that takes time for someone to accept. And some people have trouble accepting that."

Katz gets up every weekday morning at 5, does 20 minutes of calisthenics, jogs for another 20 minutes, showers and then has a breakfast of Cheerios or shredded wheat with bananas and skim milk.

He is at the hospital before 7 every day. He operates almost every morning, and always spends a few minuntes reviewing the X-ray film of the patient's heart one last time to help him focus in on that patient.

Katz may operate once or twice during the day, and he will see patients in his office at the hospital and make rounds. He gets home around 8 or 9 p.m., leaving him little time during the week for his wife and two sons, who are 3 and 6. He is in bed by 10. His wife, he says, is not "wildly enthusiastic" about the hours.

Katz's father was a child prodigy on the violin and might have had a career at that except that he decided instead to found the Dayton Philharmonic and serve as its conductor for 42 years. Katz also was a "serious" violinist in his youth. Now he takes his violin out for a vigorous practice session about once a month.

Katz has performed more than 737 heart operations. No matter how many times he operates, Katz says, each operation presents a unique problem. In Leatherman's case, the steroids she was taking made her tissue vulnerable to tearing, while the condition of her coronary arteries required special care to avoid damaging her heart during the operation.

Although he doesn't consider himself a religious person, Katz says medicine "in a way brings one very close to God because certainly we see the tremendous beauty inside the body . . . Every time one opens the chest and looks at the heart, one cannot help but be awed a little bit and one appreciates the beauty and in that way one feels closeness to a Divine Being."

Katz presents himself at the same time with self-confidence and humility: "I guess if . . . I'm a little poetic about it, I think about it in musical terms. I've practiced many years to do this. I technically have worked very hard to be as perfect a surgeon as possible. I've done my exercises. I've played my scales. I've played the little pieces. I've played the bigger pieces. Now I'm playing the concertos.

"But each time I do it, the situation is a little different, just like every time an artist plays a concerto it's a little different. I try to make it as perfect as possible . . . There is a musical equivalent. It's an improvisation, based on all your technical expertise, all your knowledge, all your knowledge of physiology. Though you use standard methods, every operation has a bit of improvisation to it, to accomplish as near perfect a result as possible."