Dr. Leila Denmark, a doctor that practiced medicine for 73 years, passed away at the age of 114. Dr. Denmark only stopped treating patients 11 years ago at the age of 103. On Sunday the doctor died at her daughter's home in Athens, Ga. of natural causes. She was the world's fourth-oldest person.

Dr. Denmark is known as the oldest practicing physician, reports the LA Times. Born on Feb. 1, 1989, the Georgia native had a passion to want to heal at a young age. After graduating from college, Denmark taught high school science. In 1924 she later enrolled at the Medical College of Georgia. According to a biography from the National Library of Medicine, Denmark was the only woman in her class of 52 students, and four years later became the third woman to earn a medical degree from the college.

According to the Atlanta Journal-Constitution, Denmark got married to John Eustace Denmark three days after graduating from medical school. Her husband died in 1991, they had been married for 61 years.

Dr. Denmark is known for her work during the whooping cough epidemic in the 1930s. Her studies helped to develop the pertussis vaccine and the modern-day DPT vaccination, reported the Atlanta Journal-Constitution.

Dr. Denmark's daughter, Mary Denmark Hutcherson said that her mother would have kept on practicing, but retired at 103 because of her eyesight. She was an excellent diagnostician and she dispensed medical advice over the phone until she was 110 because her mind was still sharp, said Hutcherson. It was her eyesight that was failing.

In 2006 Dr. Denmark revealed that living a long life isn't that complicated. You keep on doing what you do best as long as you can. I enjoyed every minute of it for more than 70 years. If I could live it over once again, I'd do exactly the same thing and marry the same man.

Dr. Stephen Coles of UCLA's department of chemistry and biochemistry believes Dr. Denmark's long life is a little more complicated than that. Coles revealed to the International Business Times that about a year and a half ago they took a DNA sample from Dr. Denmark and her daughter for research on life longevity.

Dr. Denmark's funeral is scheduled for Thursday, April 5 at 1 p.m. at the Athens First United Methodist Church.