A case is related by Breschet," in which a single ventricle and two auricles existed, but along with an imperfect inter-auricular septum. The two auricles, therefore, virtually formed one cavity. A similar case is recorded by ‘Volff,* and is remarkable from the fact that the individual in whom it was observed lived to the age of twenty-two. These hearts then do not exactly correspond to the tripartite heart of Batrachia, inasmuch as the two auricles communicate. A similar case, sliewn by Mr. Lawrence to Dr. Farre,d- explains more par ticularly the true nature of the malformation. It was a deficiency of the septa, both auricular and ventricular, the latter having been alto gether wanting ; the former consisting only of a small muscular band, which left a large fora men ovale without a valve, but the venm cavm and pulmonary veins opened into their respec tive auricles, which externally appeared to be quite separate. The ventricle communicated with the two auricles by a single ostium ventriculi, and the aorta and pulmonary artery, the en trance of the latter being somewhat contracted, arose side by side from the left part of the ventricle.
Most of the other defective malformations of the heart consist in prwternatural communica tion between the right and left cavities, resulting from various causes. 1. The communication is direct, either from an open foram( n ovate, or fmm an imperfection in the septum of the auricles or of the ventricles, or from the co-existence of all three or any two of them. 2. The com munication is indirect, the septa being perfect, but the ductus artcriosus remaining pervious.
The open foramen ovale is by far the most common of all the malformations of the heart ; numerous examples of it are now on record, as found in persons of all ages. The opening of communication varies considerably as to size, apparently according to the period of develope meat at which the arrest took place ; the di ameter of the opening ranges between two and twelve lines. We know that the size of this orifice is inversely as the size of the fmtus during intrauterine life, whence we may infer that the larger the opening is, the earlier most have been the period at which further deve lopement ceased. In many instances the valve like portions which bound this opening have acquired their full developement, and the only defect seems to be the non-adhesion of their margins, so as to close the cavity; this non adhesion again may involve the whole extent of the margins of the valves, or only a very small portion, thus leaving a large or small opening of communication between the two auricles. Such a condition of the inter-auri cular septum does not necessarily occasion that intermixture of the blood which so com monly accompanies the communication be tween the right and left cavities; and where the opening is small, of course this inter mixture is the less likely to occur. Thus every anatomist must be aware that it is not an un frequent occurrence to find an opening large enough to introduce a goose-quill in the hearts of adults who during life exhibited no derange ment of the circulation, and who died of dis eases totally unconnected with the heart. On
the other hand we are often surprised at the amazing size of the opening in the hearts of persons who have lived many years, and have shewn less disturbance of functions than the freedom of the communications between the auricles would warrant us to expect. In many of these cases the absence or mildness of sym ptoms may be accounted for by the obliquity of the passage of communication, and the overlapping of the margins of the valves, so that at times they completely oppose the flow of the blood from one side of the heart to the other, whilst at other times the passage is left more or less free. In a heart winch I lately saw in the Museum of Guy's Hospital, the circumfe rence of the open foramen ovate was equal to that of a halfpenny, (i. e. about an inch in diameter,) and yet the patient had lived to the adult period ; and in a case quoted by Dr. Farre from Corvisart, the foramen ovale was " more than one inch in diameter." Such cases strongly favour the opinion that the foramen undergoes considerable enlargement when once all impediment to the passage of the current of blood from one side to the other has been removed.* More rarely we find the fossa ovalis cribriform, and thus several small open ings of communication exist between the auricles, and sometimes in addition to the un closed foramen ovale, we have a true imper fection in the septum, as in the case related by Walter,t and another by Otto.t Imperfection in the septum ventriculorum is a much less frequent cause of the communi cation between the right and left hearts than the open foramen ovale. The opening, varying in diameter from two lines to about an inch, is situated towards the base of the septum, so that the ventricles communicate at their bases ; a fact which evidently indicates that the opening results from the progress of the de velopement of the septum being arrested near its completion, since the base of the septum is the last portion formed. The orifice of com munication generally opens upwards towards the orifices of both arteries, and is bounded inferiorly by the rounded smooth edge of the ventricular septum. In these cases the aorta opens into both ventricles and appears to arise from both ; and frequently the orifice of the pulmonary artery is contracted and more rarely obliterated, either from non-devclopement or from previous morbid action ; moreover, ap parently as a consequence of this contracted state of the arterial outlet of the right ventricle the ductus arteriosus often remains open, which, by its communication with the aorta, conveys some blood into the pulmonary arteries from that vessel ; and, as a further complication, the right ventricle is very small and appears merely as an appendage to the left; sometimes also the left auricle is very small, while the right is much dilated.