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Lampreys were often used in late-nineteenth and early twentieth-century neurobiological research because their nervous system was visible without the use of a microscope. This allowed researchers to extract intact nerve cells without damaging their electric functions, after which cross-sagittal, and transverse sections were prepared using various staining techniques. Freud, who began his career working in a laboratory for the comparative anatomy of marine life located in Trieste and run by the zoologist Carl Friedrich Wilhelm Claus (1835-1899), produced fifteen such drawings, all of which depicted the spinal ganglia of Petromyzon planeri, the brook lamprey. This drawing shows a series of ganglia and nerve plexus in the lamprey’s dorsal ridge. Freud’s penmanship reveals an emerging propensity for abstraction and anthropomorphism. Some of the ganglia, for instance, bear the incongruous mark of a smiling face instead of the more staid description of the nerve cell’s biological structures.
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