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 the morning of June 16, 1942, an old mare which had tentatively been diagnosed as a "sleeper suspect" was admitted to the Stange Memorial Clinic. The history given was that the mare had been out on pasture in apparently normal condition in the evening. The next morning she was found standing with her head down in a stupor-like condition. Her back and sides were soiled, indicating that she had suffered pain during the night.
Fisher, L. E.
"Gastric Rupture in a Horse,"
Iowa State University Veterinarian: Vol. 5
, Article 10.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol5/iss1/10