2. Inflammation of the Cardiac Structures is more Common in Acute than in Subacute Attacks of Rheumatisn2.—What is. air acute, and what a subacute, attack? An acute attack is one in which the rheumatic inflammation is both extensive and severe, affecting several joints and affecting them smartly. In other words, it is a rheumatic attack occurring in one in whom the rheumatic constitution is very marked, in the fibrous tissues of whose motor apparatus the nidus requisite to the repro duction and action of the rheumatic poison is abundantly and widely distributed, and on whom, therefore, that poison exercises a very de cided action. The more abundant and wide the distribution of the nidus, the more likely is it to exist in the heart as well as in the joints, and the more likely is the heart to be affected. As a result of its abundance, the inflammation of the individual joints is severe; as a result of its wide distribution many joints suffer. There are fifteen common seats of rheumatic inflammation—fourteen in the joints and one in the heart. The wider the distribution of the nidus the larger the number of these seats likely to suffer at one time. In this re spect the heart is in the same position as a joint; so that the wider and more abundant the distribution of the nidus the more likely is that organ to suffer. The same circumstances which make a rheu matic attack acute and severe tend also to give rise to heart compli cations, and thus is explained the fact that such complications are more apt to occur in acute cases. The heart suffers in such cases for the same reason that a large number of joints do.
Given a severe and acute rheumatic attack during whose course ten of the fifteen common rheumatic centres are affected—the heart is more likely to be among the ten which suffer than among the five which escape; the chances are two to one against it. Given a mild and subacute attack during whose course only five centres are affected —the heart is more likely to be among the ten which escape than among the five which suffer; the chances are two to one in its favor.
The effect of age in increasing and diminishing the danger to the heart we have already considered. The influence of these two agen cies, the age of the sufferer and the severity of the attack, ought to be considered conjointly ; for severe attacks of acute rheumatism seldom occur except in youth ; and nearly, if not quite, always in youth for the first time. It is probable that the severity of the attack has, in the manner just explained, as much to do with the production of the heart affection as has the youth of the sufferer.
The rheumatic constitution is not acquired, but natural—maybe inherited. A man who has it can scarcely reach the age of forty in a temperate climate without suffering from rheumatism; and he is more likely to suffer for the first time between the ages of twenty and thirty than between thirty and forty—and that simply because the former decade comes first. If his constitution be a markedly rheu matic one he will suffer severely, and the majority of his rheumatic centres will be affected. The heart is more likely to be in the ma
jority which suffer, than in the minority which escape. That organ suffers, therefore, not so much because the man is young, as because his constitution is a markedly rheumatic one; and because exposure to the rheumatic poison is too common to permit of the likelihood of his getting beyond youth without suffering from its action.
That the rheumatic constitution is less marked after middle age has already been seen. This involves diminished susceptibility to the action of the rheumatic poison; and this is common to the whole of the structures affected in rheumatism, those of the heart as well as those of the joints.
3. Rheumatic Inflammation of the Heart is Limited to the Left Side. —In considering the action of the rheumatic poison on the joints we saw that those which suffer most are the ones which enjoy the high est degree of functional activity, and are habitually subject to free and active movement—the large joints. We find the same thing in the heart; the muscles, the valves, the fibrous rings, the lining and in vesting membranes are, as regards structure and function, the same on the right as on the left side ; only those of the right side have a less degree of functional activity ; the muscular walls are thinner and less vigorous, and the valves contain less tendinous material. These structures are thinner and weaker on the right side because they have less work to do and less strain to bear. The difference between the two sides of the heart in this respect is evidenced by a reference to the contractile force of each ventricle. The walls of the left ven tricle are much stronger and thicker than those of the right, "the proportion between them in this respect being as three to one" (Quain). It follows from this that the left ventricle acts with three times the force of the right; its fibrous structures and valves have therefore to bear three times as much strain, and enjoy a correspond ingly higher degree of functional activity. " The work done by the right ventricle may be set down as one-third of that of the left" (McKend.rick.) The fibrous structures of the right side of the heart thus bear to those of the left the same relation that the fibrous structures of the small joints bear to those of the large; they have not the same degree' of functional activity, are not called upon to do so much work, and are not a nidus for the rheumatic poison. The right side of the heart escapes for the same retison that the small joints do.
Rheumatic inflammation of the heart is generally described as occurring under the three forms of endocarditis, pericarditis, and myocarditis—inflammation of the lining membrane, inflammation of the investing membrane, and inflammation of the muscular substance. For clinical purposes this is as convenient a classification as could be adopted.