HISTORY.—The history of endocarditis is restricted to modern pathology. It is not spoken of by the older medical writers. Before the sixteenth century knowledge of the structure and functions of the heart was imperfect and scanty, and its diseased conditions were altogether unknown.
The history of the pathology of cardiac disease commenced with Harvey, Lancisi, Vesalius, and Vieussens. They investigated not only the normal structure of the heart and the mechanism of the circulation, but accurately described a few of its valvular diseases.
There is little doubt but that Laennec, Senac, and Morgagni were quite familiar with the valvular diseases of the heart, but Kreisig first traced the relationship between valvular diseases and inflammation of the lining membrane of the heart.
The term endocarditis was first used by Bouillaud, who had the advantage of Laennec's discovery of auscultation. Corrigan first discovered the physical signs of aortic insufficiency. The most important advance in the pathology of endocarditis is due to the investigations of Virchow and Luschka, the former developing its sequelæ or results, the latter its histological changes. Ulcerative endocarditis is of modern date, and its literature scarcely extends back twenty years. The labors of Kirk, Virchow, Charcot et Vulpian, Moxon, Eberth, and Lancereaux are all connected with the etiology and anatomical changes of ulcerative endocarditis.
The relationship of interstitial endocarditis to valvular diseases of the heart and to cardiac murmurs is a subject which at present is engaging the attention of many medical observers.
I shall describe endocarditis under three heads:
1st, Exudative endocarditis;
2d, Ulcerative endocarditis;
3d, Interstitial endocarditis.
That the pathological changes which I shall describe may be readily appreciated, I will briefly review the anatomical structure of the endocardium.
The endocardium consists of connective tissue, with numerous elastic fibrils, covered by and continuous with a layer of flattened cells. Upon this lies the endothelial layer, which disappears in twenty-four hours after death.
Luschka regards the endocardium as continuous with all the arterial tissues, but the majority of histologists consider it a continuation of the internal membrane. Some regard the endocardium and inner coat of the arteries as analogous, since both are non-vascular and have an endothelial covering upon a connective-tissue base. As endocarditis is, for the most part, limited to the valves of the heart, a knowledge of their anatomical arrangement is important.
A transverse section of a segment of an auriculo-ventricular valve shows that upon the superior or auricular surface and upon the inferior or ventricular surface there are flattened cells and endothelium, and that next to each lies a fibro-elastic layer, the superior being the thicker. These two layers are separated by connective tissue.