1. That the artery is in general sound at the part in the front of the thigh selected for operation, while it is usually unsound in the popliteal space behind, or in the ham, where Desault operated, and Anel recommended it to be done; that operation is now abandoned on the continents of Europe and America, as well as in England. 2. That a ligature can readily be placed upon it at a distance from the disease in the fore part of the thigh, and will usually be followed by success as far as concerns the obliteration of the artery immediately below the part on which it is applied. 3. That the artery being aneurismal, the collateral branches had begun to enlarge, so as to be better able to carry on the circulation, after the supply of blood to the lower part of the limb by the main trunk had been cut off. 4. That no branches of importance are usually given off between the ligature on the artery on the fore part of the thigh and the sac of the aneurism in the ham. 5. That if such branches were ever given off, and brought the blood from their collateral communications back into the main artery below the ligature, and thence into the sac, so as to renew its pulsatory movements, they would ultimately disappear, from the impelling force not being sufficient to prevent a gradual coagulation taking place, which would soon fill up the cavity of the sac, and thus prevent its further enlargement; at which stationary point a process of removal by absorption would begin and continue, until the diseased sac with its contents had diminished, if not entirely disappeared, leaving only a trace behind of its former existence, the process thus described being frequently assisted by a commencing obliteration of the artery immediately below the aneurism. The essential point in this theory, which has immortalized the name of Hunter in surgery, depends on the integrity of the aneurismal sac, which ultimately retains, as a general rule, subject to rare exceptions, any blood which may be brought into it, either by the collateral branches from above, or from below by what may be called regurgitation, until it has become coagulated, when the sac is so filled up that no more blood can pass into it to cause its further distention, or any ulterior evil. This theory of Mr. Hunter, then so new, so beautiful in itself, was eagerly embraced by nearly all the civilized world; and surgeons were not content with applying it to cases of diseased or aneurismal arteries, to which it is especially applicable, but they extended it indiscriminately to cases of wounded arteries, to which the practice of the war in Spain proved it was inapplicable, and in which I have, since 1811, maintained it could only succeed as a matter of _accident_, not of principle. 182. The essential features of the theory opposed to Mr. Hunter, with respect to wounded arteries, and called mine, are:--