EditorialDr. Kevin Cahill, who managed to pack several careers into a single life as a leading expert on tropical diseases, a doctor to celebrities and politicians, a close adviser to Gov. Hugh L. Carey of New York and a savior to the ailing American Irish Historical Society, at the organization’s headquarters on Fifth Avenue in Manhattan during the St. Patrick’s Day parade on March 17, 2011. (Michael Appleton/The New York Times)