Abstract
Doerr's theory of the morphogenesis of transposition is discussed with special reference to recent studies by Goor and co-workers and Anderson and associates. The views advanced by all these authors coincide in three points: (a) the description of the reorganisation process occurring at the arterial end of the embryonic heart (a process called by Doerr vectorial bulbus rotation); (b) the pathogenetic interpretation of transposition as the result of an arrest of vectorial bulbus rotation; (c) the recognition of a teratological series or spectrum of anomalies pathogenetically related to transposition. Vectorial bulbus rotation is explained mainly as the result of three largely simultaneous events; bulbar shift, bulbus torsion, and truncus torsion. The spectrum of anomalies related to transposition appears as a close-knit series. Bulbar retraction does not seem to be a necessary condition for the connection of the aorta to the left ventricle.