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
It is customary to classify skin diseases as parasitic and nonparasitic. From the standpoint of accuracy in diagnosis, one is fortunate when confronted with a parasitic condition, since in these cases a complete diagnosis can be made. The macroscopic skin parasites fleas, ticks and lice are readily seen on the surface of the body in good light.
Covault, C. H.
"Common Dermatoses of the Dog,"
Iowa State University Veterinarian: Vol. 8
, Article 2.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol8/iss4/2