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
With the exception of the optic papilla, the nervous system is not subject to direct examination. Diagnosis of diseases of the nervous system must, therefore, be made by interpretation of symptoms. These symptoms are manifested as disturbances of consciousness, locomotion, senses, incoordination and motor irritation.
Donelan, B. W. and Howe, C. W.
"Central Nervous System Symptoms and Brain Damage Associated with Common Ruminant Digestive Disturbances,"
Iowa State University Veterinarian: Vol. 21
, Article 11.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol21/iss2/11