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March 7, 1925


JAMA. 1925;84(10):723-728. doi:10.1001/jama.1925.02660360005002

"Rickettsia" is the name given by da Rocha-Lima in 1916 to minute micro-organisms, with certain peculiarities, found in lice. The name, which now covers a large group of micro-organisms in insects, honors the memory of Howard Taylor Ricketts, who first described micro-organisms of this type in studies on Rocky Mountain spotted fever and typhus fever. It is impossible to formulate a wholly satisfactory definition or characterization of the micro-organisms described as rickettsiae. Already the list is a large one and is composed of three pathogenic and thirty-nine nonpathogenic micro-organisms found in diverse species of insects.1 It is not probable that all these micro-organisms are closely enough related to be included under a common name with generic or even group significance. It is very doubtful even if the three pathogenic members of this list are closely enough related to one another to warrant a common generic title. I refer now

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