Classifications have value as offering a sort of condensed résumé of existing attitudes of mind with reference to the nature and relations of the things classified, and also serve as a concrete setting forth of concepts, which, but for the effort, would tend to linger indefinitely in older settings. The nervous system was considered for a long time as a thing apart, a sort of consecrated territory, where only the initiated could be received; and as for its relations to the body, the latter largely existed to permit of those activities, while its mysteriousness was added to by being the repository for much that was not understood.
Jelliffe SE, White WA. Principles Underlying the Classification of Diseases of the Nervous System. JAMA. 2016;315(10):1059. doi:10.1001/jama.2015.17077