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282 blackwater fever, and may not return after recovery from the latter disease. In analogy with what is sometimes observed in pernicious cases of subtertian fever, some authors have suggested that the parasites, though scarce or even absent in the peripheral blood, may be numerous in some internal organ, particularly the brain. Against this a priori argument are the absence of cerebral symptoms during the attack, and the occasional negative evidence of post-mortem findings. Much has been made of the large mononuclear leucocytosis present in this disease as a proof of its malarial nature. But we now know that a similar type of leucoeytosis occurs in several other forms of protozoal disease. If blackwater fever be caused by any one of the known malaria parasites, this parasite must hare acquired its peculiarly powerful hsemolytic properties in a previous passage through an as yet unrecognized mammalian or insect host; or the subject of blackwater fever must have been exposed to some specific influence present in blackwater fever countries, but absent in other malarial districts.

2. The quinine theory.— The quinine theory of blackwater fever arose in Greece. It was first suggested by Verétas in 1858, and soon became popular amongst Greek physicians. In 1874 it was upheld by Tomaselli in Italy, and more recently it received the support of Koch. The idea that quinine might produce blackwater fever originated from a misinterpretation of the fact that the administration of quinine, even in small doses, may provoke the manifestation of blackwater fever in a patient in whom the infection is latent. As quinine, even in toxic doses, never produces blackwater fever in healthy people or in malaria patients elsewhere, its peculiar action in Africa had to be explained by a peculiar hypothetical idiosyncrasy an idiosyncrasy— which, curiously enough, is found only in certain malarious countries and not in others. Thus, the connection between quinine and blackwater fever is not one of cause and effect, but merely one of coincidence. Blackwater