While more soldiers died of disease than from battle injuries during the Civil War, a three-page document written by P.J. Horwitz, the surgeon general of the Union's Navy, proves that many members of the medical corps had little idea of how to treat a gunshot wound at the war's start. Part of the online exhibition "Passages Through the Fire: Jews and the Civil War," put together by the Shapell Manuscript Foundation, Slate shared a transcript of Horowitz's "rudimentary advice" in regards to handling injuries caused by bullets on the battlefield.
If the wound is produced by a musket ball, the patient will generally first feel a slight tingling in the part, and on looking at the seat of injury perceive a hole smaller than the projected ball, generally smooth lined, inverted and the part more or less swelled, and on examining further, if the ball has made its exit there would be found another opening, which unlike the other will have its margin everted and ragged.
Should the patient present radical symptoms of injury, one of the first things to be done is to stop the hemorrhage, if there be any, and then carefully examine the wound to see that no foreign body is lodged there in, and then after bathing the flesh in cold water, apply to the wound a piece of lint on which may be spread a little cerate, and attach it to the parts by adhesive or if the surgeon prefers it he can dip a little lint in the patient's blood and in the same manner apply it to the part, and then put the part at rest, and treat the local and general symptoms as they arrive.
Head over to Slate to read Horwitz's full treatise.