Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
On July 30, 1944, a 4-year-old Belgian mare was admitted to the Stange Memorial Clinic with a collar gall on the top of the neck. Such a gall is popularly known as a sitfast, which is caused by collar pressure on the top of the neck interfering with vascular supply to the area, resulting in necrosis. In time a definite necrotic plug or "core" forms. This pressure is frequently caused by a poor fitting collar or from the use of heavy, swinging tongue machinery.
McCreedy, Harry D. Jr.
"Care of a Sitfast,"
Iowa State University Veterinarian: Vol. 7
, Article 14.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol7/iss2/14