CLEVELAND (WJW) – He is in the Guinness Book of World Records for being the oldest practicing physician in the world.

You can read about the evolution of medicine in history books, but at 100 years old, Dr. Howard Tucker can tell you all about it firsthand.

“How does it feel to be 100 years old? Well, I really don’t feel any different from when I did when I was 99 or even 89,” he said.

His love of medicine began during undergraduate studies at The Ohio State University. The neurologist has been practicing medicine since 1947, before the invention of penicillin, MRI’s or even CAT scans.

“A lot of friends of mine retired because they could not master technology. My own attitude was, ‘damn it, I’m going to learn it,” Tucker said.

The beloved doctor still walks the halls of Cleveland’s St. Vincent Charity Medical Center, teaching residents and consulting with patients, some from three generations of the same family.

He’s always donning his signature bow tie and still leaving a lasting impression.

“I always want to talk to him more. I don’t want to stop talking with him or asking him questions. He is a vastly interesting person beyond neurology,” third-year neurology resident Priyanka Vora says.

As if his illustrious career in the medical field wasn’t enough, Doctor Tucker became a lawyer, passing the Ohio Bar exam at the age of 67.

Dr. Tucker says he tries to learn something new every day, like snow-shoeing during the winter months.

As part of his 100th birthday celebrations, he threw the ceremonial first pitch during Monday’s Guardians game against the White Sox.

He’s also received birthday wishes from former presidents, celebrities, athletes and legendary singers like Dolly Parton.

Tucker says an occasional martini, spending time with his wife of 65-years and family are the keys to longevity.

“Are you ever going to retire? I would hope not. My concept is retirement is the enemy of longevity,” he said.

Doctor Tucker served in the Navy during World War II and as Chief of Neurology for the Atlantic Fleet during the Korean War.

His grandson, Austin Tucker, is currently producing a documentary on his life and career. It will be directed by Taylor Taglianetti. The film will be released sometime next year.