Sigmund Freud (1856-1939) was an ichthyologist and carcinologist. Yes, he was! During his student years, he worked with fish and crustaceans, just in case you had thought of ichthyology and carcinology as disciplines of psychoanalysis!

As academics, we sometimes present our students completely ‘cooked’ concepts, round ideas and theories, fully unveiled pathways and mechanisms, and I am afraid that this may cause frustration among them, feeling that there is nothing novel to be discovered. Max Schultze, a German microscopic anatomist, has been said to have confessed on his deathbed in 1874 that everything was already known to science with the exception of the ‘eel question’. The reproduction of the European eel was a black hole; no gonad maturation, no egg or sperm laying and no larvae. Aristotellic descriptions endured and their conception was perceived as ‘immaculate’, eels were coming from the guts of the Earth through spontaneous generation.

One of Freud’s first courses at the University of Vienna, where he entered at age 17 to study medicine (in fact his primary intention was to study law), was ‘General Biology and Darwinism’. Carl Claus (1835-1899), director of the Institute for Comparative Anatomy taught this course. He was also the head of the newly created Royal Zoological Station of Trieste which opened in 1875. The purpose of the Zoological Station of Trieste, part of the Austro-Hungarian empire at the time, was to supply marine organisms for the museum and universities of Vienna and Graz. Claus obtained two consecutive grants for Freud, so he became one of the first visitors/users of the marine station in 1876. The goal was to find the testis in male eels. Imagine the scene: a 21-year-old student dissects and studies 400 eels for 4 months in a research station by the sea, to find close to nothing. We know now that eels only mature their gonads during their reproductive migration from European continental waters to the Sargasso seas…where reproduction is not immaculate at all. Freud’s results were of course inconclusive, and he published them in frustration in 1877. Later Freud would always hide this publication from his curriculum, a symbol of defeat and maybe the reason for him to later turn his attention to psychoanalysis and ‘male castration’. The answer to the ‘eel problem’ would have to wait until the 20th century, when a Danish researcher solved the mystery.

Picture of eel ovaries and eels at a market
Left: Micrography showing early developmental stages of oocytes in the ovaries of eels artificially matured through hormonal injections (Rojo-Bartolomé et al., doi: 10.1016/j.cbpa.2017.05.018) in the laboratory. Right: eels in Lisbon fish market. Photos by Ibon Cancio.

In 1877, Freud initiated research with Ernst Brücke (1819-1892) in his physiology laboratory in Vienna where he spent six years comparing the brains and spinal cords of humans and other vertebrates such as freshwater lampreys with those of invertebrates such as the crayfish (fresh marine material was not available). After all, the cellularity of the nervous system was not yet established, contradicting Schultze’s last words. Ernst Brücke had been an assistant to Johannes Müller (1801-1858) in Berlin. Müller, the professor of professors, was a mentor to some of the most recognised scientists in the 19th century in Prussia (Theodor Schwann, Jakob Henle, Rudolf Virchow, Robert Remak, Emil du Bois-Reymond, Ernst Haeckel, to name a few) and the father of comparative microscopic anatomy and comparative physiology. Müller’s teachings were clear: he instructed his students to compare anatomical, physiological and microscopic facts across different animal forms. In Müller’s school, the focus was marine animals, but in Vienna, Brücke and Freud were forced to focus on two freshwater species: the lamprey and the crayfish.

Picture of a sea lamprey
The sea-lamprey Petromyzon marinus in one of the fish markets in Porto, Portugal. Photo by Ibon Cancio.
Spinal ganglion of lamprey
A sketch by Sigmund Freud of the spinal ganglion of the lamprey Petromyzon planeri (now Lampetra planeri). This is a non-migrating, non-parasitic freshwater lamprey species.

Freud documented the lamprey’s spinal nerve cells and ganglia and the nerve plexus in the dorsal ridge, which he published in his first scientific publication in 1877, three months before the one on the eels. By 1882, he had published five scientific papers on the nervous system of fish and crayfish. Freud subsequently published a 37-page paper on the structure of the cells and nerve fibres of the crayfish. This paper is very important since it demonstrated that the nerve fibre, what we now call the axon, is an extension of the neurone body. Freud was able to distinguish separate fibrils following straight courses, as well as concentric loops of striae surrounding the nerves. Some authors have deemed Freud’s research work on the nervous tissue of the lamprey and the crayfish as determinant in the discovery of the neuron. Bear in mind that Santiago Ramon y Cajal obtained his first microscope in 1876 (as Freud was visiting Trieste) and published his neuron theory in 1888.

Freshwater crayfish nerve cells
Nerve cells in the abdominal and the stomatogastric ganglia of the freshwater crayfish Astacus, as published by Freud in 1882. 

In 1884, Freud initiated his work in psychiatry so a pair of inquisitive eyes were lost for the analysis of model organisms and comparative microscopy. Freud apparently enjoyed pure research and his hours in the microscope. What would have happened if he would have continued working as a comparative microscopist instead of dedicating his life to psychoanalysis? Calderon de la Barca wrote in his Life is a Dream: ‘This life is but a dream, and dreams are only dreams’, or… do dreams, especially wet ones, need to be interpreted? Maybe yes!

Bibliography of Freud on the subject of marine and freshwater creatures

Freud, S. (1877) Uber den Ursprung der hinteren Nervenwurzeln im Rückenmark von Ammocoetes (Petromyzon Planen). Sitz.Ber.d.Akad.Wiss. Wien, Math.Naturwiss.Cl. III. Abth. 75: 1-13.
Freud, S. (1877). Beobachtungen über Gestaltung und feineren Bau der als Hoden beschriebenen Lappenorgane des Aals. Sitz.Ber.d.Akad.Wiss. Wien, Math.Naturwiss.Cl. III. Abth. 75: 419-431.
Freud, S. (1878) Über Spinalganglien und Rückenmark des Petromyzon. Sitz.Ber.d.Akad.Wiss. Wien, Math.Naturwiss.Cl. III. Abt. 78:81-167. 
Freud, S. (1879). Eine Notiz über eine Methode zur anatomischen Präparation des Nervensystems. Zentralblatt der medizinischen Wissenschaft, 17/26: 468-469.
Freud, S. (1882) Über den Bau der Nervenfasern und Nervenzellen beim Flußkrebs. Sitz.Ber.d.Akad.Wiss. Wien, Math.Naturwiss.Cl. III. Abt. 85:9-46.

Sabrina Gaber
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