Ludwig Edinger: The Vertebrate Series and Comparative Neuroanatomy

Abstract

At the end of the nineteenth century, Ludwig Edinger completed the first comparative survey of the microscopic anatomy of vertebrate brains. He is regarded as the founder of the field of comparative neuroanatomy. Modern commentators have misunderstood him to have espoused an anti-Darwinian linear view of brain evolution, harkening to the metaphysics of the scala naturae. This understanding arises, in part, from an increasingly contested view of nineteenth-century morphology in Germany. Edinger did espouse a progressionist, though not strictly linear, view of forebrain evolution, but his work also provided carefully documented evidence that brain stem structures vary in complexity independently from one another and across species in a manner that is not compatible with linear progress. This led Edinger to reject progressionism for all brain structures other than the forebrain roof, based on reasoning not too dissimilar from those his successors used to dismiss it for the forebrain roof.

Keywords:

• Ludwig Edinger
• evolutionary morphology
• comparative neuroanatomy
• vertebrate series
• German Romanticism
• Carl Gegenbaur
• Ernst Haeckel

Notes

¹ Striedter cites Bowler’s The Eclipse of Darwinism (Bowler, 1983), which documents the widespread skepticism about Darwin’s mechanism of natural selection and the advocacy of neo-Lamarckianism and orthogenesis in the post-Darwinian period. Bowler’s focus on the inner progressive trends posited by such theories, together with a lack of any extensive discussion of evolutionary genealogy, can leave readers with the erroneous impression that these theories envisioned a linear genealogy. Striedter does not cite Bowler’s later Life’s Splendid Drama (Bowler, 1996), a history of evolutionary morphology that makes Darwinian genealogy a central focus of concern. This volume provides a corrective to the false impression left by his earlier work, documenting the acceptance of Darwin’s divergently branching genealogy, and the extensive late-nineteenth-century debates concerning its implications and meaning engaged in by the proponents of the various evolutionary mechanisms. Reiner’s more cautiously nuanced view of Edinger may derive from his reading of Bowler (1996), which he cites as a reference.

² Habilitation is the highest academic qualification in European academia, requiring work of greater quantity and quality than a PhD.

³ The seventh edition appears to have been the last complete, two-volume edition. The first volume of an eighth edition was published in 1911. I can find no trace of a second volume. Its publication was perhaps precluded by the outbreak of World War I in 1914 and Edinger’s death in 1918. All references to the text of the first volume are to the 1911 eighth edition, and all references to the text of the second volume are to the 1908 seventh edition.

⁴ While their work is not discussed, in Edinger’s (1908b) Vorlesungen über den Bau der nervösen Zentralorgane des Menschen und der Tiere-Zweiter Band Vergleichende Anatomie des Gehirns, Vol. 2, Karl Gegenbaur’s Vergleichende Anatomie der Wirbeltiere, mit Berücksichtigung der Wirbellosen [Comparative Anatomy of the Vertebrates, with Consideration of the Invertebrates], (1898) and H. G. Bronn’s Klassen und Ordnungen des Tierreichs [Classes and Orders of the Animal Kingdom], Vol. 6 (1907) are cited.

⁵ Morris is unmistakably a Darwinian. He begins his paper with an explanation of Darwin’s mechanism of natural selection but makes no mention of neo-Lamarckian or orthogenetic alternatives.

⁶ This claim is, of course, woefully at odds with modern understanding. A wide variety of animal species are now known to have sensory abilities excelling those of humans in a wide variety of ways. Many animals can detect features of their environment (ultraviolet light, polarized light, ultrasound, electrical fields, etc.) to which humans are completely insensitive.