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
The structure and physiology of birds differs in many respects from that of mammals.
Hewitt, E. A.
"Comparative Physiology of Birds,"
Iowa State University Veterinarian: Vol. 2
, Article 6.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol2/iss3/6