Blane was appointed Physician to the Fleet (1779–1783) and accompanied Rodney, initially to pursue the Spanish squadron besieging Gibraltar and engaging them at the Battle of Cape St. Vincent, and then to the West Indies. Blane did much to improve the health of sailors by improving their diet and enforcing proper sanitary precautions. He demanded monthly reports from other ships' surgeons which enabled him to build up a detailed picture of the high levels of sickness that affected the squadron. Despite James Lind's 1753 publication of "A treatise on scurvy", which established the importance of fresh fruit and vegetables in preventing scurvy, the Admiralty had not implemented his recommendations, and scurvy remained a significant cause of sickness in the Fleet. Blane published a pamphlet for the benefit of ships' surgeons in 1780 entitled "On the most effective means for preserving the health of seamen, particularly in the Royal Navy." He advocated the use of citrus juice as a preventative and cure for scurvy in the squadron and eventually, as Commissioner of the Sick and Wounded Board, persuaded the Admiralty to go against the theories of the medical establishment and introduce lemon juice as daily addition to the naval diet in 1795. Later lemons were replaced by limes which could be obtained from Britain's Caribbean colonies, and for this reason, "limey" became a common slang word for a British person.