Using a variety of experimental animals, Ferrier demonstrated that various neurologic functions were controlled by separate parts of the cerebrum and that damage or loss of that part created an irrevocable and particular deficit. He showed that these areas were much more discrete as one ascended the phylogenetic scale and that, accordingly, effects of brain damage in rabbits, dogs and cats etc. could not be compared to those in monkeys, apes and human beings. Clarke & O’Malley, The Human Brain and Spinal Cord, pp. 513-14. This paper became the basis of Ferrier's book, The Functions of the Brain (1876).

Ferrier may be said to have laid the foundations of our knowledge concerning the localization of cerebral function. His book includes his earlier work published in the West Riding Lunatic Asylum Reports. Digital facsimile from the Internet Archive at this link.