Aequanimitas was one of Sir William Osler's most famous essays, delivered to new doctors in 1889 as his farewell address at the Pennsylvania School of Medicine, prior to transferring to Johns Hopkins. It was published in the same year and in 1904 appeared in his collection of essays titled Aequanimitas with Other Addresses to Medical Students, Nurses and Practitioners of Medicine. A second edition was produced in 1906, and a third in 1932. In the essay, Osler advocates two qualities "imperturbability" and "equanimity", which he defined as "coolness and presence of mind under all circumstances". Between 1932 and 1953, Eli Lilly & Company distributed more than 150,000 copies of the third edition to medical graduates. Through the years Osler's ideal of "Aequanimitas" has been analysed by various academics. Daniel Sokol, medical ethics and law expert, reasons in the British Medical Journal in 2007, that whatever interpretation is made of Aequanimitas, it "tackles head-on a timeless question: what makes a good doctor?". Publication The essay Aequanimitas was an essay by Sir William Osler, delivered to new doctors on 1 May 1889 as his farewell address at the Pennsylvania School of Medicine. It was published in the same year. Aequanimitas refers to staying calm and composed. In the essay, Osler advocates two qualities "imperturbability" and "equanimity", which he defined as "coolness and presence of mind under all circumstances". 1904 and 1906 In 1904, Aequanimitas was published by H.K. Lewis in Aequanimitas with Other Addresses to Medical Students, Nurses and Practitioners of Medicine, a collection of his essays. A second edition was produced in 1906 by P. Blakiston's Son & Co. in Philadelphia, and H.K. Lewis in London. Eli Lilly & Company Following Osler's death, an expanded version of the book appeared as a third edition in 1932. It omits the essays "A Way of life", "A man's redemption of man" and "The old humanities and new science", and became more widely available than the previous editions. Between 1932 and 1953, Eli Lilly & Company distributed more than 150,000 copies of the third edition to medical graduates. These volumes were not all the same. There were at least seven different publications in English and one in each of Spanish and Portuguese. There were variations in the type of paper, book size, title page, information on the spine, and printing information. There were also differences in the congratulatory letters from Eli Lilly, placed in