This is a disease whose right to a position amongst the infectious may still be disputed by some, and which has, in the past, been regarded variously as an intoxication arising frofn faults of excretion, and as of some nervous origin. The general aspects of the disease are those of a specific fever due to a general intoxication, and the local manifestations also point to the general distribution by the blood of a poison which has, as is usual with poisons, certain local affinities. The painful affection of the joints, which is such a prominent symptom as to give very much of its character to the disease, is not to be regarded as indicating that the primary seat is in, or in the neighbourhood of, the joints. No infective agent is known, and there is no such local centre as exists in diphtheria, typhoid fever, and other foriiis, in which it may be supposed that the infection has its seat. It is probable, therefore, that it is present in the blood, but it cannot be said whether it is deposited in the various local lesions or not. The disease is not infectious from person to person, nor is its mode of propagation known, but there are interesting facts showing connection with particular localities, and also its prevalence amongst the inmates i if particular houses. Whilst there are the symptoms of a general intoxication, there are also local inflammations affecting chiefly certain fibrous membranes. In the localities affected the appearances indicate that, besides the direct influence of the toxic substance, friction plays a part in the production of the inflammation. Thus the localities themselves, namely, the joints, the pericardium, and the valves of the heart, are exposed to constant friction from the movements of the body, and further, in the valves of the heart, the lesion is in a striking manner restricted to those parts which are exposed to impact of neighbouring portions during the closure of the valves (see under Acute Endocarditis).

There may be a mixed infection in this disease. The regular and extended distribution of the lesion in acute endocarditis indicates the action of a dissolved toxine, or a very abundant infective agent in the blood. On the other hand, pyogenic microbes may, taking advantage of a breach of surface, attach themselves to a particular part of a valve, but this need not be in a portion exposed to friction, and it may occur when the fever has completely subsided (see under Ulcerative Endocarditis).