Notes on the Muscular Architecture of the Left Ventricle

N EARLY three hundred years ago (1669) in his book Tractus de Corde, Richard Lower offered the first detailed description of the muscular anatomy of the ventricle.l* His drawings show separate overlapping layers, rather like the layers of an onion, each layer consisting of differently directed muscle fibers. Since his day, many anatomists, perhaps most definitively Mall,3 have repeated his dissections and have altered his schemata only in details. As a result, today the illustrations of ventricular myocardial architecture in all anatomy textbooks are essentially elaborations of Lower's original drawings. Yet, for generations, medical students (and more recently cardiac surgeons) have compared with dismay the textbook illustrations of the heart with the organ they hold in their hands, for no such layers are to be seen. It is ironic that Lower, who did so much in his day to liberate medicine from medieval dogma, should himself be the origin of a dogma for later generations. The reason why the Lower schemata fail to be accurate or useful is related to the fact that the only conceptual tool available to him in his day was plane geometry. As he expressed in his Tractus, ".according to Geometry's laws, the straight line is the guide to the