Even when the frank and open progress of the disease through the joints of the body has come to an end, the enemy is still lying in wait and reserving his most deadly assault. Distressing and crippling as are the effects of rheumatism upon the joints and tendons, its most deadly and permanent damage is wrought upon the heart. Fortunately, this vital organ is not attacked in more than about half the cases of acute rheumatism, and in probably not more than one-third of these are the changes produced either serious or permanent, especially if the case be carefully watched and managed. But it is not too much to say that, of all cases of serious or "organic" heart disease, rheumatism is probably responsible for from fifty to seventy per cent. The same germ or toxin which produces the striking inflammatory changes in the joints may be carried in the blood to the heart, and there attack either the lining and valves of the heart (endocardium), which is commonest, or the covering of the heart (pericardium), or the heart-muscle. So intense is the inflammation, that parts of the valves may be literally eaten away by ulceration, and when these ulcers heal with formation of scar-tissue as everywhere else in the body, the flaps of the valves may be either tied together or pulled out of shape, so that they can no longer properly close the openings of the heart-pump. This condition, or some modification of it, is what we usually mean when we speak of "heart disease," or "organic heart disease." The effect upon the heart-pump is similar to that which would be produced by cutting or twisting the valve in the "bucket" of a pump or in a bulb syringe. In severe cases of rheumatism the heart may be attacked within the first few days of the disease, but usually it is not involved until after the trouble in the joints has begun to subside; and no patient should be considered safe from this danger until at least six weeks have elapsed from the beginning of the fever. The few cases (not to exceed one or two per cent) of rheumatic fever which go rapidly on to a fatal termination, usually die from this inflammation of the heart, technically known as endocarditis. The best way of preventing this serious complication and of keeping it within moderate limits, if it occurs, is absolute rest in bed, until the danger period is completely passed. Now comes another redeeming feature of this troublesome disease, and that is the comparatively small permanent effects which it produces upon the joints in the way of crippling, or even stiffening. To gaze upon a rheumatic knee-joint, for instance, in the height of the attack,--swollen to the size of a hornet's nest, hot, red, throbbing with agony, and looking as if it were on the point of bursting,--one would almost despair of saving the joint, and the best one would feel entitled to expect would be a roughening of its surfaces and a permanent stiffening of its movements.