An examination of the brain, to ascertain the truth of the supposition above mentioned, was relinquished with regret, but this was impracticable; for the want of time on these occasions frequently obliged us to content ourselves with investigating the state of the most important parts. This must serve as our apology for not oftener relating the appearance of all the principal organs; yet it should be observed, that such methods have been employed to ascertain with accuracy the most interesting morbid phoenomena, as would satisfy the most scrupulous anatomist.
The tricuspid valves and the semilunar valves of the pulmonary artery had lost their healthy transparency, but were not otherwise diseased. In all the above cases these valves had been found without important derangement of their structure; a circumstance not less remarkable, than difficult to be satisfactorily explained. The basis of the mitral valves was marked by a bony projection, which nearly surrounded the orifice of the ventricle; the valves themselves were thickened, and one of them was smaller than the other. The semilunar valves of the aorta were lessened in size, and somewhat thickened. One of them was ossified sufficiently to annihilate its valvular function; the others were slightly. The aorta under the valves was semicartilaginous, ossified in one small spot, roughened by fleshlike prominences in others, entirely deprived of the smoothness of its internal coat, and in size proportioned to the heart.
The parietes of the heart were thicker than those of a healthy heart, but thin when compared with its whole volume; whence it follows, that the cavities were enlarged. That of the left ventricle was disproportionately larger than the others, but no difference of size could be ascertained between the auricles. When a cavity of the heart is situated in the course of the circulation immediately behind a contracted orifice, it seems probable that the contraction may have an important influence in originating the enlargement or aneurism of that cavity; but, where there is no contraction of an orifice, what is the obstruction which impedes the free discharge of blood from the heart, and causes the first yielding of its parietes? Perhaps a violent simultaneous action of many muscles, from great exertion, may, during the systole of the heart, impede the passage of the blood through the arteries, drive it back upon the valves of the aorta, and resist the heart at the moment of its contraction. If the parietes of the heart yield, in one part, it is easy to conceive a consequent distension of the remainder to any degree; for, during the systole of the heart, the columnæ approximate, till their sides are in contact, to protect the parietes of the heart; but, if these be distended, the columnæ can no longer come in contact with each other, and the blood passing between them will be propelled against the parieties, and increase their distention. The left ventricle being thus dilated, the mitral valves will not be able to completely cover its orifice, and part of the blood will escape from the ventricle, when it contracts, into the auricle when dilated with the blood from the lungs; and this undue quantity of blood will gradually enlarge the auricle. A resistance will arise, from the same cause, to the passage of the blood from the lungs, thence to that from the right ventricle and auricle, and thus these cavities may become enlarged in their turns. When an ossification of the aorta, or of its valves, exists, there will be a resistance to the passage of the blood from the left ventricle, either by a loss of dilatability in the artery, or a contraction of the orifice by the ossified parts. In either case, the blood will reflow upon the heart, and dilate the left ventricle, as in _case the first_, and others; and, if the mitral valves be thickened and rigid, the left auricle will be more dilated than in a case of simple aneurism of the left ventricle, as appeared also in the _first case_.