The disease is due to the implantation of pathogenic microbes on the endocardium. Pyogenic micrococci constitute the form of microbe, but the source of these is sometimes obscure. The disease has been observed to occur in the course of a number of acute febrile affections. It is met with in pyaemia, puerperal fever, acute rheumatism, small-pox, etc., and Osier has pointed out that in a large proportion of cases acute pneumonia has been the primary disease. There are, however, cases in which no definite connection with any other disease can be traced. In the case of pyaemia and puerperal fever the source of the microbes is not far to seek, but in the other cases it is more difficult. In order to the occurrence of ulcerative endocarditis, it seems probable, from the results of experiments on animals, that some previous damage to the endocardium is usually to be inferred. This damage may be the result of a simple endocarditis, and the way being thus opened, the microbes may find entrance.
The micrococci from cases of ulcerative endocarditis have been cultivated on nutrient media in order to determine their characters. They have been found to possess the usual characters of the micrococci of suppuration. Thus the Staphylococcus pyogenes aureus and albus and the Streptococcus pyogenes have been found (Weichselbaum).
Experiments have been made by injecting cultures of these microbes into the blood of rabbits. It has been found that as a rule their simple presence in the blood is not sufficient to cause ulcerative endocarditis, but that when the valves are at the same time injured then this affection supervenes (Orth and Wissokowitsch). On the other hand, it was found by Ribbert that, when an emulsion was made of a culture of these microbes on potatoes, the injection of the emulsion was followed by ulcerative endocarditis. Apparently small particles of potato adhered to the endocardium and planted the microbes.
In its local manifestations this form presents some resemblance to simple acute endocarditis. The disease affects, usually, the valvular structures, and produces an enlargement and roughening of them. But there is not the same localization along the lines of contact, the process generally developing in a defined area, sometimes removed from the valve. Again, the disease, as the name implies, is a much more destructive one, the parts concerned breaking down more readily (see Fig. 226). In this way perforation or aneurysm of the valve more readily occurs. Sometimes an actual suppuration manifests itself in the valvular structures, but the frequent passage of the blood prevents any •considerable accumulation of pus. The ulceration sometimes passes to the muscular wall of the heart, especially when the patch of ulceration is away from the valves, and in this case the destructive process spreads rapidly in the myocardium, and a distinct abscess may be the result. In this way also an acute aneurysm of the heart may supervene.
Fig. 226. - Ulcerative endocarditis affecting the aortic valve. There is a local lesion with marked prominence and a large perforation.
In their more intimate characters, also, the conditions in ulcerative endocarditis differ from those in the ordinary simple form. As the accompanying figure (227) shows, there is a very marked infiltration of the valvular structures with round cells, almost a suppurative condition. This is immediately overlaid by a fibrinous coagulum, as in the case of simple endocarditis, but mixed with the fibrine there are colonies of micrococci which give quite a striking character to the layer. The appearances in distant parts are evidence that pieces are frequently carried off from the valves, and looking to the soft character of the superficial parts we are not surprised at the occurrence of Multiple embolism.
Fig. 227. - Portion of valve in ulcerative endocarditis, a, Fibrine with colonies of micrococci; the colonies are indicated by the roundish clumps; b, endocardium becoming raised by inflammatory infiltration; e, elastic layer of endocardium; c, round cells infiltrating endocardium, at d, passing into superficial layer of fibrine and micrococci, x 22.
Perhaps the most striking feature in this disease is the occurrence of Metastatic abscesses in distant parts. These are found in the heart itself, in the spleen, in the kidneys, in the skin, etc. They are everywhere of small size, and usually in large numbers. These abscesses are obviously related to emboli carried off from the endocardial lesion,, and lodged in the finer arteries or capillaries. The accompanying figure (228) represents a small artery in the midst of an incipient abscess in the kidney. It is seen that its calibre is plugged by a material in-which are occasional masses of micrococci. At the distal part the wall of the artery is obscure, apparently from necrosis, and the vessel is buried in an enormous aggregation of round cells. The micrococci are frequent in the capillaries and Malpighian tufts, but not generally with obvious inflammation; apparently they are in that case of recent development, possibly to some extent post-mortem, and their products have not had time .to produce inflammation.
Fig. 228. - From the kidney in ulcerative endocarditis. An artery is shown, plugged with a dark material containing micrococci. Around these are myriads of leucocytes which are infiltrating the necrosed wall of the vessel and the kidney tissue around, x 90.
We have aeen that the micrococci have, locally, an intensely irritating action, and that necrosis of the tissue attacked is a common result. It is probable that they also produce changes in the constitution ■of the blood. Patients affected with this disease frequently present, like those in pysemia, a yellow colour of the skin approaching to that of jaundice. The probable explanation of this is, that the blood-corpuscles undergo solution, and the colouring matter stains the skin. Besides that, we often have little ecchymoses of the skin, and small Haemorrhages in the pia mater, and even in the brain substance. These have been found associated with the presence of colonies of micrococci in the capillaries, and are to be ascribed to the action of these in weakening the wall, and allowing escape of blood.