When these tubercles are sufficiently numerous to become confluent, large masses may be formed, which undergo the same retrogressive changes of Caseation and calcification.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
At first the swelling is covered by epithelium; in time Caseation takes place, the epithelium gives way, and an open sore is formed.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson