“His Work has implications to this day”

As a researcher, Hermann von Helmholtz covered a lot of ground. That much is clear from the translation of his dissertation from Latin, which includes the description of basic principles of the nervous system that hold true to this day. An interview.

Prof. Helmut Kettenmann, author of the reading tip

Helmut Kettenmann, a neuroscientist at the Max Delbrück Center for Molecular Medicine in the Helmholtz Association, has translated the dissertation Hermann Helmholtz wrote in Latin as a 21-year-old student at the Friedrich-Wilhelm-Universität Berlin in 1842 into German and English as a version with an introduction and notes, having teamed up with classical scholar Julia Heideklang from the Humboldt-Universität and neurobiologist Joachim Pflüger from the Freie Universität Berlin. Their book was released in August.

Helmholtz conducted research into the nervous systems of insects, spiders, crabs, snails and worms, comparing their external structures and the microstructure on the inside. He described nerve cell fibres and identified the basic structure of ganglia in the ventral nerve cord. He picked up on a number of similarities between the central nervous systems of vertebrates and invertebrates.

How did you come up with the idea of translating a dissertation written in Latin almost 170 years ago?

I actually accidentally discovered that Helmholtz had published a paper on neuroscience in Latin. Keen to find out more about his work in this field, I soon realised that nobody had ever translated that dissertation into another language. It has been a good 45 years since I studied Latin and a machine translation was no good whatsoever. So I got in touch with the Helmholtz Association and shared my belief that this text needed to be translated. I was given the funding and started working with Julia Heideklang, a classical scholar who works mainly with Latin scientific texts from the same period. Joachim Pflüger is an expert in the nervous system of invertebrates, whilst I specialise in vertebrates.

What were your next steps?

Julia Heideklang started off by translating the text literally. We then worked together to edit the text so that it was written in a language that a scientist would be able to understand. The terminology has all changed over time. For example, we didn’t start talking about neurones for another 50 years after the dissertation was written.

How long did it take you to turn your original idea into a finished book?

I sent my proposal to the Helmholtz Association in November 2020 and the book was released on 1 August.

Why hadn’t the dissertation been translated before?

Back then, all dissertations were published in Latin as standard. It wasn’t until the 1860s that this rule was relaxed and dissertations could also be published in German. Basically, nobody else had come up with the idea to go back and translate Helmholtz’s work.

Was it worth it? Had Helmholtz written anything of relevance?

He had written a truly groundbreaking paper. It’s hard to believe that he had this level of insight and made these kinds of discoveries all that time ago. It’s even harder to believe that this piece of work remained undiscovered for so long.

What does his dissertation tell us in the modern day?

We need to go back in time to answer that question. Back then, neuroscience was a very new discipline. Henle and Schleiden had only come up with cell theory around four or five years earlier, in 1838. That theory is based on the important discovery that all tissues are made up of individual cells. And it led to the question of how nervous systems are structured. The first-ever image of a nerve cell had only been published in 1836, which was just six years earlier. Unsurprisingly, then came further fascinating questions... As humans, we use our brains for self-awareness. And we can well imagine that the same can be said for cats and dogs. But what about leeches and earthworms? Do they have a nervous system? Do they even need one? What would it look like if they did? As part of his dissertation, Helmholtz examined a long list of invertebrates, including earthworms, crayfish and mussels, and analysed their nervous systems under a microscope.

And what did he find?

He found that the nervous systems of all these invertebrates have exactly the same basic structure as those of vertebrates, including humans. They are made up of nerve cells, intersected nerve fibres and nerve centres, which take the form of collections of nerve cells called ganglia in invertebrates. The human central nervous system consists of the brain and the spinal cord, but we do also have ganglia in our peripheral nervous system, controlling our bowel movements and so on. If you perform a full comparison, you find that the entire animal kingdom shares the same blueprint for the basic nervous system. Helmholtz came up with this hypothesis in his dissertation. That is its main point. He was the first person to systematically examine the nervous systems of various creatures under a microscope.

So the translation doesn’t just exist because it bears the Helmholtz name and can be put on display on a shelf somewhere by the staff at the Helmholtz Association. Does that mean that researchers can take away findings and suggestions even now?

I would go so far as to say that it should be compulsory reading for neuroscience students.

Was Helmholtz’s work really so exceptional for his time?

Definitely. He promoted a vision that previously simply did not exist. Or had been articulated with such clarity. His work resonates right through to the present day.

In what form?

In the 1960s and 1970s, when I was starting out in neuroscience, it was common practice to use invertebrate systems as models when explaining basic principles in the discipline. Basically, all the paradigms, such as how memories are stored, are similar in every creature from a snail to a human. Research into any fundamental mechanism can be conducted on invertebrates because the basic structure of their nervous system – the whole molecular structure and molecular mechanism – is identical to that of vertebrates like us humans. I worked on the inner workings of crayfish during my days as a student and found that the basic mechanisms are exactly the same. The fundamental principles behind the fact that invertebrate systems can be used as models for the human nervous system actually originate from work done by Helmholtz.

Did the translation start to read more fluently once you’d got into the swing of it?

Let’s just say that it was a challenge. It was tricky enough to even work out what he meant from his descriptions. We had to really think about the perspective from which he was seeing things. That’s why I asked Joachim Pflüger to get involved in the project as an expert in the nervous system of invertebrates. If you aren’t familiar with it and somebody tries to describe it in flowery language, it’s hard to decipher what Helmholtz actually meant. Unfortunately, he didn’t have the funds to illustrate his work since it could only be done using expensive copperplate etching back then.

What do we know about how the original dissertation in Latin was received? Was it often cited?

Dissertations didn’t tend to be cited much at the time anyway. The inner circle would have been familiar with it for certain. For example, the well-known physiologist and anatomist Johannes Müller rallied all the students from this Berlin school, including Rudolph Virchow, who founded the field of cellular pathology, and Emil du Bois-Reymond, who measured the electrical activity of the nervous system. The fundamental principles at the heart of neuroscience and the first image of a neurone all came about during that era. In Berlin. The would of course all have known one another. They would have read about the research in Latin, but it wouldn’t have been accessible to the next generation. One important thing to note from this time is that microscopy had only just been systematically introduced to research and teaching. And Berlin was the hub where an entire industry was created with the purpose of producing microscopes.

So we can assume that there is other interesting work out there dating back to this period.

Yes, we can assume that is the case.

In this case, a famous name helped to save some of that work from being lost forever.

Absolutely! If it hadn’t been for the name, I would never have come across the dissertation in the first place.

Interview: Thomas Röbke

Heideklang, Julia/Pflüger, Hans-Joachim/Kettenmann, Helmut: De fabrica systematis nervosi evertebratorum. Die kommentierte Dissertation von/Commented Dissertation by Hermann Helmholtz, 2021, wbg Academic.

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