This week (3 Mar to be precise) marks the founding of the Medical Corps of the United States Navy, in 1871. The US Navy was a relative latecomer to the establishment of a permanent corps of physicians to serve the health of sailors.
In the west, mention of physicians serving aboard naval vessels goes back to Homer. The Roman navy is believed to have paid its surgeons double the army pay to entice them to serve in the less prestigious military arm. During the late middle ages, the maritime republics of Italy routinely posted surgeons aboard ships, and during the Crusades, naval surgeons established shore based facilities for the care of injured and sick sailors. Medical Officers of Genoa and Venice were responsible for issuing health certificates to sailors of these navies; these officers also established port quarantine (from Italian quarantina giorni–“forty days”) procedures for prevention of imported contagion, especially plague.
In the modern era, the Spanish and French were early to adopt standing naval medical establishments, maintaining naval hospitals in colonial territories. While the British Royal Navy had surgeons aboard ships from the 15th century, they did not form what might be recognized as a formal medical corps until 1805, when for the first time, surgeons of the Navy were granted rank similar to other military officers, and a distinguishing uniform.
From the beginning, U S navy regulations specified a unique uniform for medical officers, but they were not granted rank-equivalence with their line officers until around the time of World War I. Prior to that, medical ranks were Assistant Surgeon, Passed Assistant Surgeon, Surgeon, Medical Inspector and Medical Director.