Scientific neurology and the history of the clinical examination of selected motor cranial nerves.

The content of the neurological examination of the motor cranial nerves is a reflection of the current understanding of the neuroanatomy and clinical neurophysiology of the brain stem. The history of the neuroanatomy of the cranial nerves extends from Galen's investigations c. 200 CE to the determination of the innervations of the facial nerve by Charles Bell in the early 19th century. Scientific clinical neurophysiology first appears in the work of John Hughlings Jackson in the mid- to late 19th century. The modern model of the organization and function of the nervous system results in a clinical examination that can be called neurological. The codification of the technique of the neurological examination of the cranial nerves mirrors the institutional and social history of neurology and is reflected in the changing role of neurology textbooks in the 19th and 20th centuries. The texts develop through stages of classification, pedagogy, reference, and institutionalization and illustrate the development of a specialized medical discipline.