The electron microscopy of endocardial fibroelastosis.

It has been shown (Still and Boult. 1956) that when teased preparations of the endocardium in congenital endocardial fibroelastosis are studied by electronmicroscopy the superficial zones are largely composed of a material bearing little resemblance to collagen or elastic tissue, as the histological appearances suggest, but having the morphological characters of fibrin. We proposed therefore that this material's presence must be duie to the incorporation of surface deposits into the endocardium. Teased preparations cannot, however, represent accurately either the exact position of fibres, or their relative amount in the endocardium, and only thin sections can do this satisfactorily. A study of such sections is described in this communication, and it seems to bear out our previous conclusions.