If the swelling is soft, it should be punctured at the lowest point, and afterwards the cavity should be Syringed with Lugol's solution.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
The cavity should be Syringed out with an antiseptic solution.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
When softening occurs in the center of a hard mass and fluctuation can be felt between two fingers pressed on different parts of such softening, it should be freely opened to let out the putrid pus, and the cavity should be Syringed often with antiseptic solution.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler