The _upper_ end of an artery retracts on being divided, and this retraction is accompanied by a contraction of the cut extremity of the vessel, which assumes the shape of the neck of a French wine-bottle or Florence oil-flask. The contraction is confined in the first instance to its very extremity, so that the barrier opposing the flow of blood is formed by this part alone. The contraction, however, goes on increasing for the space of an inch; it is usually filled up with an internal coagulum of a round, pyramidal shape, adhering firmly to the contracted end of the artery, loose at its apex, and extending frequently as far as the first collateral branch, but rarely under any circumstances beyond two inches; the very orifice of the artery on the outside being in a few days covered by a layer of a yellowish green-colored substance or fibrin, which indicates its situation in a remarkable manner. Some of these processes are continued even after the external wound has healed; the artery generally goes on diminishing and contracting as far as it is useless, so that of three or four inches, from one to two may be impervious, the remainder being contracted, although still permeable by a probe. An accompanying nerve, where there is one, would do the reverse, the cut extremity would become enlarged or bulbous, gradually diminishing as it is traced upward, until it regains its proper size. The processes adopted by nature for closing the lower end of a divided artery of the size of the femoral at the inferior part of the thigh are somewhat different from those employed at the upper or opposite extremity. The retraction or contraction of the _lower_ end of a divided artery is neither so perfect nor so permanent as at its _upper_ end, and the small internal coagulum is in many instances altogether wanting, or very defective in its formation. The closure of the lower orifice being less perfectly accomplished than of the upper, it is the more likely to suffer from secondary hemorrhage, which may be distinguished from that from the upper end of the artery at an early period after the accident, by the _venous color of the blood, and from its flowing or welling out in a continuous stream, as water rises from a spring, and not with an arterial impulse_.