The German physician Korbinian Brodmann (1868-1918) was diverted from plans to enter general practice by a long convalescence during which he worked at a sanatorium for nervous diseases. After advanced studies in neurology, neuroanatomy, pathology, and psychiatry, he began an investigation of the comparative anatomy of the mammalian cortex at the Neurobiological Laboratory of the University of Berlin. Earlier workers had divided the cortex into six principal layers on the basis of their proportions of pyramidal, stellate, and fusiform cells. Using the newly developed staining technique of Nissl, Brodmann distinguished about 50 zones of the cortex on the basis of subtle differences in cell type, size, density, and lamination, and correlated his anatomic findings with studies on localization of function in humans, subhuman primates, and other mammals. His cortical map and numbering system, published in 1909, became standard methods for distinguishing areas of cortex, and are still widely used by clinical neurologists and neurosurgeons. Although later workers have published revisions of his work, subdivided his areas, and substituted letters for his numbers, modern experimental methods have largely vindicated his cortical localizations, both anatomic and functional. see also figure at cerebral cortex.