We have already seen that, except in the foetus, this form of disease is uncommon as a primary lesion. In cases of acute or chronic endocarditis with well marked lesions on the left side, however, there are very often distinct indications of inflammation in the valves of the right heart.

Relative insufficiency of the tricuspid valve, although secondary, is often of considerable consequence on account of the effects to which it leads. We have seen that in mitral disease the right ventricle usually dilates and hypertrophies, and with this change in the ventricle the orifice widens. The valve may thus be unable to cover the enlarged orifice, and become insufficent. In other forms of dilatation and hypertrophy of the right ventricle, as in that due to obstruction to the pulmonary circulation, the same thing may occur. The tricuspid orifice normally admits readily three fingers up to the first joints, and when enlarged it is not uncommon to meet with cases in which it admits four, five, six, or even seven fingers. If the valve is thus incompetent to close the enlarged orifice the blood will, during the systole of the ventricle, regurgitate into the auricle. The wave will be propagated irwto the veins of the neck, and there will probably be an aggravation of existing congestion of the systemic veins.

It need only be added, that if chronic endocarditis attacks the tricuspid or pulmonary valves, it may produce results similar to those effected in the mitral and aortic. The tissue here, however, is less substantial to begin with, and the inflammation is usually much less intense, and so the changes are rarely of any great consequence.