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
Cannibalism in the chicken is frequently initiated by the presence of bleeding blood vessel hamartias in the skin. These defects in the growth of blood vessels are very common in the chicken. It is a heritable disease of the White Leghorn chicken. Since all of the major families of White Leghorns have originated from the same basic stock, all have this heritable defect. At times the anomaly becomes a problem in certain families of birds.
Monlux, William S.
"Blood Vessel Hamartias in the Chicken,"
Iowa State University Veterinarian: Vol. 23
, Article 2.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol23/iss3/2