In 1764, a new variant appeared. Advocated by Dr David MacBride and Sir John Pringle, Surgeon General of the Army and later President of the Royal Society, this idea was that scurvy was the result of a lack of 'fixed air' in the tissues which could be prevented by drinking infusions of malt and wort whose fermentation within the body would stimulate digestion and restore the missing gases. These ideas received wide and influential backing, when James Cook set off to circumnavigate the world (1768–1771) in , malt and wort were top of the list of the remedies he was ordered to investigate. The others were beer, Sauerkraut (a good source of vitamin C) and Lind's 'rob'. The list did not include lemons.