Dilatation of the orifices of the hcart.—As natural result of dilated cavities we meet with dilated orifices of the heart, and the enlarge ment of which again produces in many cases insufficiency of the valves. Bouillaud gives the measurement of the auriculo-ventricular orifice (which is the most liable to dilatation) in three hearts ; in one it measured five inches in circumference, and in another four inches three lines, while in a third the dilatation was stated to be so great that the tricuspid valve could not be closed.
Aneurism of the heart.—A diseased state of the heart occurs not unfrequently, strongly analogous to that which under the same name is so well known as occurring in the arterial system. Most of the varieties too of arterial aneurism find their analogues in the heart: thus we have, 1. the aneurism by simple di!a tation, or true aneurism, resulting from partial dilatation of one of the heart's cavities; 2. the false aneurism or that resulting from rup ture of one or more of the textures entering into the formation of the heart's parietes ; 3. we find the dissecting aneurism analogous to that remarkable form of arterial aneurism first described by the late Mr. Shakelton ; 4. not improbably, we also meet with what is analogous to the varicose aneurism, and may be designated spontaneous varicose aneurism of the heart. To the zeal and acuteness of Mr. Thurnam * morbid anatomists are much in debted for his having arranged, compared, and classified a considerable number of cases of aneurismal dilatations connected with the heart, either observed by himself, or preserved and recorded by others, whence he has been able distinctly to prove the analogies above-men tioned, and by which much light has been thrown upon those forms of disease.
The partial dilatation of one of the cavities, or true aneurism, is by far the most com mon of the varieties above-mentioned. In its early stage this disease consists in little more than a bulging of the wall of the ventricle or auricle in a certain direction ; as this in creases a pouch or sac is formed, which com municates with the heart's cavity by a more or less narrow opening. In some cases this sac does not extend beyond the external surface of the heart, nor would it be detected, were the anatomist to content himself with merely ex amining the exterior, it is as it were lodged in the fleshy substance of the ventricular parks; but in other instances a tumour is formed pro jecting considerably beyond the exterior. As in
arterial aneurisms, the sacs frequently contain laminated coagula, and, as might he expected a priori, the larger the cavity and the narrower its orifice of communication, the more abun dant is this lamellar deposit. One or more aneurismal sacs may belong to the same cavity: thus, in fifty-two out of fifty-eight cases col lected by Mr. Thurnam, only one aneurism existed in each ; but in four cases two were met with in each ; in one there were three, and in another four incipient aneurisms. In two instances, Mr. Thurnam states, it is not improbable that two sacs which were originally distinct had coalesced, so as to form a single aneurism, and in another case three sacs ap pear to have united in this way. We find the aneurismal pouches of all sizes: in nine of the cases referred to in Mr. Thurnani's memoir, the size might be compared to that of nuts; in twenty, to that of walnuts ; in seven, to fowl's eggs; in fourteen, to oranges; and in nine cases, it almost or quite equalled that of the healthy heart itself. We cannot always satisfactorily ascertain what textures enter into the formation of these sacs; however, in the majority of cases, the three structures of which the heart's parietes are composed are found in the walls of these sacs; in others the muscular tissue has disappeared, atrophied probably by the pressure, and the wall is composed only of the endocardium and pericardium, and in others again the endocardium is wanting, and the muscular fibres and the pericardium are the only component elements.* In some cases the wall of the sac is strengthened by an ad hesion formed with the loose layer of the peri cardium.
These aneurisms are always in connection with the left ventricle or left auricle; very rarely however with the latter, and never with the right cavities. In the paper already quoted from, Al r. Thurnam has collected references to fifty-eight cases of aneurism of the left ven tricle, and eleven of the left auricle. All parts of the ventricle are liable to aneurismal dila tation, but it occurs most frequently at the apex : next in frequency it is found at dif ferent points of the base; less frequently still it occurs in the lateral walls at situations in termediate to the two last-named, and very rarely it is met with in the intcrventricular septum.