In cases of traumatic aneurism the operation should be something like the following:--A free incision should be made into the tumour, dividing it in its long direction; the contents should be rapidly scooped out, and a finger placed on the bleeding point, just at the upper corner of the sciatic notch. This will at once stop the hæmorrhage till the vessel can be secured. This sounds easy enough, and has been done several times with success. Thus, John Bell, by an incision two feet long, as he tells us in his hyperbolical language, was enabled to tie the vessel in the case of the leech-gatherer who had punctured the artery by a pair of long scissors. Carmichael of Dublin used a smaller incision, removed one or two pounds of clots, and tied the vessel, in a case of wound by a penknife.[6] Now, though both of these cases were eventually successful, both patients lost during the operation a very large quantity of blood; John Bell's especially could not be removed from the operating-table for a considerable time after the operation. The period at which the great loss of blood took place was the interval after the incision was made, and before the artery was exposed to view, _i.e._ the interval in which the surgeon was busy dislodging the clots from the cellular membrane, the sac of the false aneurism. The procedure devised by Mr. Syme to obviate this difficulty, and which was put in practice by him in several very trying cases, is best given in his own terse description of an operation in a case of traumatic gluteal aneurism:--