WE WISH TO REPORT a new method that we have used for successful ligation and division of the thoracic aorta. Doctor Halsted' nearly succeeded in occluding the vessel by external pressure, and both Doctor Reid2 and Doctor Pearse3 succeeded in blocking it by inserting foreign bodies into the lumen. Doctor Pearse4 also reported successful occlusion after external application of a band of cellophane in I940. It was of great interest to us that Doctor Halsted had been able to constrict completely any of the large blood vessels except the thoracic aorta. After careful reading of his very complete papers, it seemed to us that there were probably two reasons for his failure. First, the change in the caliber of the vessel had always been made very abrupt and, second, that it had usually been produced by a very unyielding substance, namely, an aluminum band. We, therefore, outlined a series of experiments in which the constriction was to be made in the form of an hourglass, using for the purpose materials that would give to a certain extent with the pulsation of the vessel. We later changed the form of the constriction to the shape of a funnel with the large end pointing toward the heart. In the early experiments preserved fascia lata was used, but Doctor Hewitt and I found, as other people had previously reported (Reid2 and Pearse4), that this substance soon disintegrated and allowed the vessel to widen its lumen. We next tried a double layer of the best quality silk cloth, but this was not satisfactory because it tended to wrinkle up like an accordion and also caused too much local tissue reaction. In time, the vessel opened under the cloth, allowing pressure to be reestablished in the aorta below the band before collateral circulation had been established. In order to prevent this from happening, we conceived the idea of applying a section of ordinary stationer's rubber band over the silk band, as a second stage. Finally, after about two years' work with only one successful experiment, we abandoned all other materials in favor of rubber. It seemed best for several reasons: It could be easily molded to the desired shape by mattress sutures; it gave well with the pulsation of the vessel, and caused very little tissue reaction by comparison with the other materials. We soon found that it was necessary, no matter what the material used, to produce the constriction always in two and usually in three stages in order to keep the pressure above the bands high enough to produce sufficient collateral circulation. At first we waited six weeks to two months between operations, but found that this was too long because the vessel opened too widely. We then tried a series where a lapse of only two weeks was allowed, but found that
