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A doctor at the Queen Elizabeth Hospital Birmingham does his rounds on the wards in 2006. Wednesday is National Doctors' Day. Getty Images

They're intelligent, they're selfless, and they're the ones you should be thanking on Wednesday.

It's National Doctors' Day, an annual observance aimed at appreciating physicians everywhere. The holiday started in 1933 in Winder, Georgia, and since then it's been held on March 30 — the first anniversary of a doctor using ether anesthesia during surgery, according to the Southern Medical Association Alliance.

As of 2013, the United States had about 767,000 physicians under the age of 75, and demand was climbing. ModernHealthcare.com reported that, due to population growth and extended life spans, experts predicted a shortage of up to 90,000 doctors by 2025.

Whether you're an aspiring health care professional, a patient or simply a fan of your physicians, take some time Wednesday to let them know you care. Check out these inspirational quotes about medicine, collected from nursingschools.net, QuoteGarden and TodayInSci:

"In nothing do men more nearly approach the gods than in giving health to men." — Marcus Tullius Cicero

"In the sick room, ten cents' worth of human understanding equals ten dollars' worth of medical science." — Martin H. Fischer

"The art of medicine consists in amusing the patient while nature cures the disease." — Voltaire

"The doctor should be opaque to his patients, and like a mirror, should show them nothing but what is shown to him." — Sigmund Freud

"Medicine sometimes snatches away health, sometimes gives it." — Ovid

"A physician is obligated to consider more than a diseased organ, more than even the whole man — he must view the man in his world." — Harvey Cushing

"Nurses dispense comfort, compassion, and caring without even a prescription." — Val Saintsbury

"A doctor, like anyone else who has to deal with human beings, each of them unique, cannot be a scientist; he is either, like the surgeon, a craftsman, or, like the physician and the psychologist, an artist. This means that in order to be a good doctor a man must also have a good character, that is to say, whatever weaknesses and foibles he may have, he must love his fellow human beings in the concrete and desire their good before his own." — W. H. Auden

"The good physician treats the disease; the great physician treats the patient who has the disease." — William Osler

"Only the healing art enables one to make a name for himself and at the same time give benefit to others." — Chinese Proverb

"Only a life lived for others is a life worthwhile." — Albert Einstein

"The mark of a true doctor is usually illegible." — Anonymous

"He is the best physician who is the most ingenious inspirer of hope." — Samuel Taylor Coleridge

“Tenderness and kindness are not signs of weakness and despair, but manifestations of strength and resolution.” — Gibran Khalil Gibran

"The dedicated doctor knows that he must be both scientist and humanitarian; his most agonizing decisions lie in the field of human relations." — David B. Allman

"Drugs are not always necessary. Belief in recovery always is." — Norman Cousins

"Wherever the art of medicine is loved, there is also a love of humanity." — Hippocrates