Mechanistic analysis of infarction along the boundary zones between the major arterial territories (watersheds) in the brain is herein describes as an example of a scientific explanatory shift. The two explanations for the pathogenesis of watershed infarction were both logically deduced from radically different empirical laws of fluid mechanics. The first explanation became the orthodox or received view only until incompleteness necessitated the development of an alternative and autonomous explanation which accounted for the empirical phenomenon that the orthodox explanation could not logically infer. Since this explanatory shift emerged to maintain completeness, and used empirical laws (Bernoulli's law and the Fahraeus-Lindqvist effect) as antecedents for the logical deduction of consequents which were empirically testable by experiment, it is suggested that the explanatory shift was of the Hempelian-type.

ISSN 0823-2105

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    Société canadienne d'histoire de la médecine