Having thus, however imperfectly, sketched the pathology of the arterial system in con nexion with the use of the ligature, it will be necessary to revert to other forms of disease, which have hitherto been postponed, in order to permit the introduction of the subject of secondary haemorrhage, and that the practical arrangement of aneurism and its consequences, both fortunate and otherwise, might be as un interrupted as possible.
Aneurismal varix.—In the year 1761, Dr. William Hunter* directed the attention of the profession to a disease that had not been before observed, one not indeed very formidable in its consequences, but exceedingly curious as to its exciting cause and subsequent progress. When an artery and vein lying in close con tact are transfixed by a cutting instrument in such a manner that the aperture in one shall exactly correspond with that of the other ; and when subsequent inflammation has so glued and fastened these apertures together, that, whilst a mutual transmission of blood between the vessels is freely permitted, not a drop will be allowed to escape in any other direction, a disease is formed, to which the discoverer gave the name of aneurismal varix. All and each of these several conditions are absolutely indispensable, and there are so many chances of their not being fulfilled in a case of wounded artery, that the infrequency of the disease may be easily explained. It does, however, occasionally occur, and for obvious reasons will most generally be found in the arm as a consequence of phlebotomy.
Soon after the infliction of the injury that has been the cause of the disease, a small tumefaction is observed in the vein ; its ap pearance is irregular and knotted, but it is soft, yielding, and disappears on pressure. On laying the finger on it, a peculiar thrilling sen sation is perceptible, and on applying the ear, a whizzing noise is heard, very much re sembling that occasioned by a fly inclosed in a small paper bag. These phenomena dis appear on either current of blood being in terrupted by pressure on the artery above or on the vein below : at the same time that the tumour subsides a little, (though it soon regains its original size) and the peculiar noise is no longer heard. If the disease is allowed to advance uninterruptedly, the calibre of the artery above the point of communication be comes enlarged, but it is diminished below : the vein also enlarges chiefly in the direction of the current of its blood, rarely in the opposite, and then but very slowly. Another interesting
circumstance is, that the peculiar thrill is heard and felt all over the dilated portion of the vein, at a distance from, as well as in the immediate neighbourhood of, the point of communication between the two vessels. It seldom produces any inconvenience that can not be remedied by the use of a moderately tight bandage, and if thus managed in time never requires a severer treatment.
From the circumstance of pressure, either on the artery or vein, diminishing the size of the tumour and removing the thrilling sen sation it imparted, it may be fairly inferred that both these phenomena are produced by the meeting of the two currents of blood, and their mutual resistance to the escape of either from its proper vessel. And further, it is ob vious that if the disease should by any chance prove troublesome or alarming to the patient, its growth might be checked and its progress altogether stopped by permanently obliterating the canal of either the artery above or the vein below : but no operation that a surgeon would be justified in undertaking can remove the tumour, inasmuch as the blood still will con tinue to flow into and through the enlarged vein. The dangers of secondary hemorrhage after an artery is tied, or of venous inflam mation if the other vessel is tampered with, ought to inculcate the greatest caution, and it may be easily understood why in such cases Dr. Hunter thought it advisable not to interfere.
This disease must, in the great majority of instances, be the result of accident, and its probable si tuation has been already pointed out, but it is also possible that it may appear as au idiopathic affection without any previous violence. Some years since a young female applied at the Meath Hospital as an out patient, in whom aneurismal varices existed between every artery and vein in the body that lay in a state of approximation to each other. In the neck, in several parts of the arms, the thighs, &c. the peculiar thrill and sound were remarkably distinct and plain. She did not seem to experience much uneasiness, nor could any probable exciting cause be assigned for such a singular form of disease. She had pre viously suffered from syphilis and been sub jected to irregular mercurial treatment, but it would be scarcely fair to assume as the cause of a solitary specimen of disease in one indi vidual, influences that operate so very differ ently on others.