Soemmerring's work on the nervous system: a view on brain structure and function from the late eighteenth century.

Samuel Thomas Soemmerring (1755-1830) was an encyclopaedic anatomist and one of the most experienced and renowned neuro-anatomists in the late eighteenth century. His description and illustration of the brainstem with its still accepted classification of cranial nerves (1778), the discovery of the acervulus in the epiphysis (1785), his demonstration of the crossing of the optic nerve fibres (1788), and of the macula lutea in the retina of the eye he had discovered in 1791, won him great recognition. Probably, unaware of Francesco Gennari's (1750-1797) and Félix Vicq d'Azyr's (1748-1794) observation, Soemmerring in the final years of the eighteenth century saw the broad white line running through the calcarine cortex of the occipital lobe. Soemmerring's comprehensive textbooks on the nervous system Vom Hirn and Rückenmark, 1788/1792, and Hirn- und Nervenlehre as part of his anatomical handbook Vom Baue des menschlichen Körpers, 1791/2nd edn, 1800, comprise all the knowledge in the field of neuro-anatomy at his time. Although the structure-function relationships mentioned are generally hypothetical, Soemmerring was convinced that mental faculties are executed in certain brain regions. In his treatise Uber das Organ der Seele, 1796, he localized the functions of the soul within the cerebrospinal fluid, which should come into close contact with the demonstrated and presumed nerve endings in the walls of the ventricular cavities. This last attempt of a synthesis of anatomy and metaphysics provoked passionate discussions and was criticised for epistemological reasons. Nevertheless, Soemmerring had moved the brain into the centre of the science of man what led to far-reaching consequences in the complexity of the discourse about man.