In those wounds to which the surgeon’s care is called, the primary hemorrhage is ordinarily small in quantity and of short duration—a sudden flow at the moment of injury, and nothing more. When a part of the body is carried away by round shot or shell, the arteries are observed to be nearly in the same state as they are found to be in when a limb is torn off by machinery. The lacerated ends of the middle and inner coats are retracted within the outer cellular coat; the caliber of the vessel is diminished, and tapers to a point near the line of division; it becomes plugged within by coagulum; and the cellulo–fibrous investing sheath, and the clot which combines with it, form on the outside an additional support and restraint against hemorrhage. When large arteries are torn across, and their hemorrhage thus spontaneously prevented, they are seldom withdrawn so far but that their ends may be seen protruding and pulsating among the mass of injured structures; yet, though the impulse may appear very powerful, further hemorrhage is rarely met with from such wounds. There is more danger of continued hemorrhage from wounds by pieces of shell, as the arteries are liable to be wounded without complete transverse section of their coats. The sharp edges, less velocity, and oblique direction in which the fragments usually impinge sufficiently explain this difference. It comparatively rarely happens that arteries are cut across by musket–bullets, either round or conical. The lax cellular connections of these vessels, the smallness of their diameters in comparison with their length, the elasticity as well as toughness of the tissues forming their coats, the fluidity of their contents, and, in consequence of all these conditions, the extreme readiness with which they slip aside under pressure, act as means of preservation when these important structures are subjected to such danger as the passage of a musket–ball in their direction. Endless examples occur where the ball appears to have passed through in the direct line of the artery, so that it must have been pushed aside by it to have escaped division. Mr. Guthrie mentions a case where a ball even opened the sheath of the femoral vessels, and passed between the artery and vein, in a soldier at Toulouse, without destroying the substance of either vessel. So close was the ball, and such contusion was produced, together with, doubtless, injury to the vasa vasorum, that the artery became plugged with coagulum, and obliterated. A preparation of these vessels is in the museum at Fort Pitt. Another case is mentioned by Mr. Guthrie, where the direction of a ball between the left clavicle and first rib, and permanent diminution of the pulse in the arm on the same side, led to the conclusion that the subclavian had escaped direct destruction by the missile in a similar way.