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
A purebred 22-month-old Shorthorn bull was admitted to Stange Memorial Clinic on Oct. 4, 1950. The history indicated that the animal had normal sexual desire but was unable to protrude his penis.
Clausen, D. W.
"An Unusual Type of Sterility in a Bull,"
Iowa State University Veterinarian: Vol. 13
, Article 9.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol13/iss1/9