MILTON — His life’s tenth decade is on the horizon, but if Fred Ernesti closes his eyes, he can still see the inquisitive little blond-headed kid he once was, the boy in Argentina who a long time ago stopped a train on its tracks when an early-and-crude experiment unexpectedly yielded billows of white smoke.

He can effortlessly recount another teenaged procedure that involved a frog, a Gillette razor, and a lesson that could have — but didn’t — steer him toward a career in accounting or auto mechanics.

Let’s just say the little green patient didn’t make it.

“I took things out and sewed him up,’’ Dr. Ernesti is telling me the other day in the study of his home here as late afternoon golden sunshine dances across the Neponset River in the near distance. “And, of course, several days later, the damn thing was found dead.’’

Botched chemistry experiments and dead frogs could not derail Fred Ernesti.

And that applause you hear is coming from grateful patients who are happy to wait for a doctor who will not be rushed, a physician who looks into their eyes instead of a computer screen, an esteemed and decorated endocrinologist — a rare breed who blends modern medicine with an old-world touch.

How rare?

He’s a guy who gives his patients his home phone number and encourages them to call. I’m here to serve you, he tells them, not the other way around. And something else: He’s not afraid to have some fun.

When Emma Odenweller climbed up on his examining table here the other morning at his office adjacent to Beth Israel Deaconess Hospital-Milton, Dr. Ernesti placed the ends of his stethoscope in his ears.

“Let me listen to that ticker,’’ he told Odenweller, his patient for more than 40 years.

There was a pause. And then this: “Either my instrument isn’t working, or you’re dead.’’

Odenweller smiled the smile of someone who’s heard it all before.

“He tells you the truth,’’ the 92-year-old patient said. “And if I don’t like it, I can answer back. He’s very honest. You can get mad at him. But we’re still friends.’’

Friends. It’s a word that’s rarely used in the same sentence as your primary care physician in an era of overbooked schedules, where face time with your doctor can be dictated by the algorithms of medical insurance bean counters.

“The problem with some younger doctors is they don’t have a relationship with the patients,’’ Ernesti said. “They’re looking at the screen. And people are complaining and that’s a good thing that they’re complaining. Because, eventually, they are going to change the system. And the system depends on you.’’

The son of a Standard Oil Company engineer, Fred Ernesti followed a circuitous path to the United States — a path that wound from his native Argentina to Aruba, where he lived until age 10, and back to Argentina, where he earned his medical degree and a ticket to the United States for a residency in 1956.

When he landed at Logan, he saw snow for the first time and detected something else about Boston that he discussed with the cab driver who drove him to Carney Hospital, the first stop on his long medical itinerary.

“This is kind of a quiet city, isn’t it?’’ Ernesti asked the cabbie.

“And then he said something that is so true of Boston,’’ the doctor told me. “He said, ‘You’ll find it very quiet on the surface, but it’s burbling inside.’ I’ll never forget that. And he was right.’’

His career in endocrinology lay ahead of him in those early years at Carney Hospital, but a more life-changing event was more immediate, more tectonic, more intense.

It happened on a hospital elevator.

Julia Hegarty, a hospital social worker, stepped aboard, and the young doctor pretended to open a book that, he discovered to his later embarrassment, he had been holding upside down.

“Holy Mother of God!’’ Ernesti recalls thinking at that moment. “I don’t know what I did to deserve you.’’

You can’t tell the story of Fred Ernesti without the woman who would become his lifetime partner, the mother of their six children, the keeper of his calendar and his checkbook. The woman, who two years after her death, remains the love of his life.

Her picture adorns the wall over the desk of their youngest daughter, Cecilia Ernesti-Bailey, who manages her father’s medical office. It sits on the night stand in his bedroom on Adams Street here.

“When she died, I was stroking her hand for five hours and then suddenly she went away,’’ Dr. Ernesti, his voice softening, recounted. “And I said. ‘Where the hell did you go? You’re here someplace. It’s impossible that you’re not here. It’s absolutely impossible.’’’

He rarely visits the cemetery, he said, because her spirit is alive. It’s alive in the vigorous practice he still maintains. It’s alive in their children, who see in him what she saw in him.

Their oldest child, Bill, was stopped by a local cop years ago, driving too fast after an uncle’s wedding. “I didn’t stop at a stop sign,’’ he recalled. “And I said, ‘Oh, great. I’m going to get a ticket.’ The cop comes up: ‘Are you Dr. Ernesti’s son? I’m going to let you go because of your father.’’’

“Everybody loves him,’’ the son said of the father. “If he doesn’t know something, he finds out about it. He questions everything. He’s like a detective. Sherlock Holmes. The combination of intellectual curiosity and doggedness — that’s a powerful force.’’

At age 88, Ernesti is still making rounds at the hospital that has been his professional home for 30 years now, a place where he has earned a reputation as a medical wise man.

“He’s at the pinnacle,’’ said Dr. Scott Lutch, a longtime cardiologist who has known Ernesti for 30 years. “I say to these young 30-year-old doctors, ‘Listen, you guys, you make sure you get to know him.’ I tell them that because they’ll never meet anybody like him in their whole lives as physicians.’’

Or as another colleague, Dr. Richard Delany put it: “He’s the most amazing person I’ve ever met. Truly a man for all seasons.’’

Indeed, to spend a day with Fred Ernesti is akin to taking a post-graduate course in the classics with a dose of aphorisms for good measure.

The guy quotes from Shakespeare’s “Macbeth,’’ the Gospel according to St. Mark, Hippocrates, and Cervantes’s “Don Quixote.’’ He listens to Beethoven and Shostakovich. His own art adorns the walls of his house, finely fashioned works in watercolor and pencil and ink.

“He hasn’t lost his fastball,’’ said Dr. John Mahoney, chief neurologist at the Milton hospital. “He’s really competes against illness. He doesn’t give up. If he were an athlete, he’d be Larry Bird. He’s very humble. He loves medicine. He is medicine. He could never retire.’’

Retirement is not part of Fred Ernesti’s self-crafted prognosis.

There are poems to be read, patients to see, lessons to learn.

As he showed me around his study the other day, he opened a packet of reading material — newspaper clippings, cutting-edge medical journals — that awaited him that night. There are books on his night stand.

There are places he still wants to see.

“I’m very much aware that knowledge is ephemeral,’’ he told me. “One day you have it. It’s like a tree that blossoms. If you don’t nourish that tree, it will disappear entirely.’’

And so when the morning comes, he’ll be back in his office here having real — and long — conversations with patients who’ve become old friends.

And his daughter Cecilia will be down the hall, buzzing him, knocking on her father’s door, trying fruitlessly to keep those trains running on time.

Thomas Farragher is a Globe columnist. He can be reached at thomas.farragher @globe.com.