This disease is said to be more frequent in the horse than the one which has just been referred to. When it occurs in association with rheumatism, it is more likely to end fatally in a short time than ordinary inflammation of the pericardial membrane, in consequence of the liability of the valves to undergo thickening, and the blood to coagulate upon them and upon the surfaces of the heart's cavities.
Symptoms indicative of endocarditis of the ordinary kind have been differently described by different observers.
The physical signs of the disease are: excited action of the heart, and the presence of certain sounds which are described as endocardial murmurs. The friction or rubbing sound which is recognized in pericarditis will not usually be present.
It is somewhat remarkable that little or no pain is manifested during the progress of the malady. The pulse at the commencement is frequent and full in its beat, afterwards becoming feeble and irregular. Fever is sometimes very pronounced, and at others it tends to assume a low subdued form. The results to be apprehended are deposits within and upon the valves and round about some of the orifices, thus interfering with the passage of the blood, and leading to obstruction and the formation of large fibrinous clots. These are not unfrequently broken up into small fragments by the movements of the heart, some of which are carried along the course of the circulation, and may thus lead to fatal obstruction by blocking up vessels in important organs.
The malignant forms of the disease, associated with the formation of abscesses and ulcerations, have only now and again been recognized in the horse.
When the disease is complicated with an attack of rheumatism, salicylic acid and its salts must be resorted to and persevered with to check the progress of the disease. Perfect rest must be enforced and every form of excitement avoided. The bowels should be gently acted upon as required by the administration of small closes of sulphate of magnesia, and any manifestation of heart weakness must be met by the careful employment of digitalis and ammonia.