Topographic Anatomy and Histology of the Valves in the Human Heart.

An accurate knowledge of the structure of the valves in the human heart is of prime importance for at least three very practical reasons. The first is that the various anatomical peculiarities in the valve leaflets suggest an explanation for at least some of the mechanical components entering into the localization of inflammatory, as well as of degenerative (atherosclerotic) processes in these sites. Secondly, the insight into pathological processes thus obtained helps one differentiate these lesions from one another. Thirdly, one is better able to cope with the long disputed question as to whether or not blood vessels or myocardium normally et in valves. This is not a merely academic question, myocardium having been implicated by various authors as the source of the alleged exitence of blood vessels in normal valves. The descriptions of the valves found in the literature are difficult to follow because the best ones are given by workers who limit themselves to only one or two valves and, since the terminology used is often different, confusion results. As an illustration of this, one may mention that the same layer of tissue in the valve is called "Klappenplatte" by Seipp, "Mittelschicht" by Beitzke, "Grundstock" by Koniger, "Lamina Fibrosa" by Tandler, "Klappenskelet" by Benninghoff, and by other investigators is referred to by number. Perhaps the greatest source of dispute lies in the fact that, with rare exceptions, no attempt is made to set definite limits to the valve. It may be said at once that this factor alone is largely responsible for the controversy on the extent to which myocardium has been found in valves and, because of this, on the frequency with which blood vessels have been found in the valves. * This study was aided by a grant from the Lucius N. Littauer Foundation. Received for publication June 22, 1931. t Moses Heineman Fellow in Pathology.