Vox Meditantis

Angelina Fanny Hesse (1850–1934) introduced agar to bacteriology in 1881, solving a problem that had stalled the entire field: how to cultivate pure bacterial cultures without the medium melting or being degraded by the very organisms growing upon it. Her suggestion – drawn from childhood memories of Indonesian cooking – enabled Robert Koch to isolate the tuberculosis bacterium and fundamentally transformed microbiology from guesswork into rigorous science. Despite agar’s ubiquity in laboratories worldwide, Hesse received neither credit nor compensation during her lifetime, her contribution erased by the structures that rendered women’s unpaid scientific labour invisible.

Welcome, Mrs Hesse. Thank you for speaking with us. It’s remarkable to have you here, particularly as so many microbiologists use your innovation daily without realising its origin. How does it feel to know that agar remains the foundation of bacteriology more than 140 years after you suggested it?

It is… gratifying, I suppose, though peculiar to consider. In my time, the matter seemed quite straightforward – Walther had a problem with his gelatine cultures liquefying in the summer heat, and I simply recalled what our neighbour had taught my mother about keeping jellies firm in warm weather. I did not think of it as an innovation, merely as applying what one knows to a difficulty at hand. To learn that the substance is still used, and so widely – that is unexpected. Though I confess, I never imagined it would become so important. It was only agar-agar, after all.

That modesty is striking, particularly given the scale of what your suggestion accomplished. But let’s go back to the beginning. Tell us about your childhood in New Jersey, and how you came to know about agar in the first place.

I was born in New York City in 1850, the eldest of ten children, though we lost five of my siblings when they were quite young. My father, Gottfried Eilshemius, was an import merchant – quite prosperous – and my mother, Cécile, was of Swiss descent. We lived at Laurel Hill Manor in North Arlington, and it was a bustling household. As the eldest daughter, I was expected to help my mother with the younger children and with the household management from an early age. She taught us all – my sisters and I – about cooking and housekeeping. It wasn’t considered education in the formal sense, but we learned a great deal.

The agar came from a neighbour, a Dutch woman who had emigrated from Java. She used it in her cooking to make jellies and puddings that would hold their shape even in the heat of summer. My mother was fascinated by this, as our own jellies made with gelatin would often fail in warm weather. The neighbour showed us how to use agar-agar – that’s what she called it, the Malay name – and it became something my mother and I both used regularly. I remember thinking it quite clever, this substance from seaweed that behaved so differently from animal gelatin.

So this was purely domestic knowledge, passed between women in a kitchen setting.

Entirely. There was no thought of laboratories or science. It was simply practical knowledge for managing a household. When I was fifteen, my parents sent me to finishing school in Neuchâtel, Switzerland, where I studied French and home economics. Again, nothing resembling scientific training. I learnt languages, deportment, household management – what was considered appropriate for a young woman of my station. The irony, of course, is that this “unscientific” education proved more valuable for solving a scientific problem than any formal training might have done.

You met Walther Hesse in the early 1870s. What drew you to him, and what did you understand about his work at that time?

I first met him – or rather, was introduced to him – through his brother Richard when Walther was visiting New York. But we truly became acquainted when my sister Eugenie and I were travelling in Germany in 1872. He was a physician, earnest and dedicated, and we found we could talk for hours. We became engaged in 1873 and married the following year in Geneva.

At that time, I understood his work in general terms – he was concerned with public health, with understanding disease. But I didn’t comprehend the technical details. That came later, when we moved to the Erzgebirge mountains where he worked as a doctor in the uranium mines, and then to Strehlen, a suburb of Dresden. As his work evolved, I became more involved, though always informally. There was no position for me, no title. I was simply his wife, and it was expected that I would assist him.

“Expected that you would assist him” – yet you developed significant technical expertise. Can you describe the work you actually did in Walther’s laboratory, and later in Robert Koch’s?

Certainly. I prepared culture media – mixing the nutrients, pouring the plates, ensuring everything was sterile. This required considerable care and precision. One must heat the solutions to the correct temperature, avoid contamination, maintain consistent technique. I also cleaned and sterilised the laboratory equipment, which was tedious work but absolutely essential. A single contaminated flask could ruin days of experiments.

The other significant portion of my work was creating scientific illustrations. Walther used my drawings in his publications – detailed watercolours of bacterial colonies as they appeared under the microscope and on agar plates during different growth phases. This required both artistic skill and thorough understanding of what I was observing. One must know the difference between bacterial growth and contamination, understand morphology, recognise the salient features worth recording. I painted perhaps eleven such illustrations for his 1906 publication on intestinal bacteria, showing the colonies in accurate detail and colour.

That sounds remarkably similar to what we’d now call a medical technologist or laboratory research assistant – yet you worked unpaid.

Yes, I received no compensation. It would have been unusual for a married woman of my class to accept payment for work done in her husband’s laboratory. Such labour was considered part of one’s wifely duties, not professional work deserving remuneration. At the time, this seemed unremarkable. One did not question such arrangements.

Let’s turn to the summer of 1881 – the moment that would change bacteriology. Set the scene for us. What was the problem Walther and Koch were facing?

It was dreadfully hot that summer. Walther was working in Robert Koch’s laboratory in Berlin, studying microbes in the air, and the heat was causing terrible difficulties. They had been using gelatine as a solidifying agent mixed with nutrients to create a surface on which bacteria could grow. This had advantages over earlier methods – slices of potato, coagulated egg white – because gelatine was transparent, allowing one to observe the colonies’ appearance clearly.

But gelatine had two critical weaknesses. First, it would liquefy – melt into a gooey mess – at temperatures above room temperature, which meant summer experiments were nearly impossible. Second, many bacterial species produce enzymes that digest gelatine directly, turning the medium into a liquid puddle. When Walther needed to incubate cultures at 37 degrees Celsius – the temperature of the human body, essential for studying pathogens that infect humans – the gelatine simply wouldn’t hold. He was tremendously frustrated. I remember him describing it as “maddening liquefaction”. The experiments would be ruined just as they reached the crucial stage.

And you suggested agar. Was it truly as simple as a conversation over a meal?

More or less. One day Walther asked me, in some exasperation, why the jellies and puddings I made remained solid even in warm weather. We were eating lunch, I believe. I told him about agar-agar – that I had been using it for years in the kitchen precisely because it doesn’t melt at room temperature the way gelatine does. I suggested he might try it in his cultures. He was immediately interested and reported the idea to Koch.

Walk us through the technical properties that make agar superior to gelatine. What exactly happens at the molecular level that allows it to withstand higher temperatures?

I can tell you what we observed empirically, though the molecular explanations weren’t available to us then. Agar remains solid at temperatures up to 100 degrees Celsius – far higher than gelatine. It doesn’t melt until you heat it quite intensely, and then it only sets again when cooled to about 30 to 45 degrees, creating what’s called a large hysteresis – a significant gap between melting and setting temperatures. This meant one could sterilise it by boiling or autoclaving without destroying its properties.

Additionally, bacteria cannot digest agar. They lack the enzymes required to break down the polysaccharides. This was crucial – it meant that even bacterial species that would reduce gelatine to a liquid puddle within hours could grow on agar without degrading the medium. The culture would remain intact for days, even weeks, allowing for extended observation and subculturing.

Finally, agar is transparent when set, allowing excellent observation of colony morphology – colour, shape, texture, the characteristics by which different species can be distinguished. And it could be stored for extended periods without deterioration.

So in one substance, you had thermal stability, resistance to enzymatic degradation, transparency, sterilisability, and stable storage. Did you recognise immediately that this would solve all of Koch’s problems?

Not entirely, no. I knew it would withstand the heat better than gelatine – that was obvious from kitchen use. But whether it would support bacterial growth, whether it could be sterilised without harm, whether it would remain transparent – those were questions that required testing. Walther and Koch conducted those experiments. I simply provided the initial suggestion. The rest was their work to validate.

Koch used agar to isolate Mycobacterium tuberculosis in 1882, work for which he later received the Nobel Prize. How did you feel when you learnt of that success?

Pleased, of course. Tuberculosis was – is – such a terrible disease, killing one in seven infected people in Germany at that time. That Koch could identify the bacterium causing it, could prove its role definitively, was momentous. I understood that agar had contributed to that achievement by allowing him to culture the organism reliably. But I also understood that Koch’s genius lay in his methodology, his rigorous experimental design, his staining techniques. The agar was merely a tool. An important tool, certainly, but one element among many.

Yet in Koch’s 1882 paper announcing the discovery, he mentioned agar in just one sentence, without crediting you or Walther for its introduction. Neither you nor Walther ever published about agar yourselves. Why not?

Several reasons, I think. First, Walther was not assertive about priority or credit. He was a careful, methodical man, more concerned with the work itself than with recognition. It simply didn’t occur to him to publish a separate paper about the medium. He assumed others would note its advantages and adopt it – which they did.

As for myself, I had no standing to publish. I was not a scientist, had no formal training, held no position. Who would have published a paper authored by a housewife? The suggestion that I might submit work under my own name would have seemed absurd to everyone, myself included at that time. The knowledge came from cooking, from domestic work – not from the laboratory. In the hierarchy of knowledge, such origins were not valued.

Yet that “domestic” knowledge solved a problem that had stumped the entire field of bacteriology. Linnaeus himself had classified all bacteria under the order “Chaos” because they couldn’t be reliably isolated and studied. Your kitchen knowledge ended that chaos.

Yes, though I didn’t think of it in such grand terms. It’s strange, isn’t it? The presumption that only formally educated men working in official laboratories can produce scientific insight. Meanwhile, the solution was known to women making desserts in Java, transmitted through Dutch colonial networks, applied in immigrant kitchens in New Jersey. The knowledge was there all along. It simply wasn’t valued because of where it came from and who held it.

Speaking of Java and colonial networks – the agar itself travelled through empire. It came from seaweed harvested by Japanese and Malay communities, brought to the Dutch East Indies, made its way through colonial commerce to Dutch emigrants in America, and then to German laboratories. Do you have thoughts about that trajectory?

At the time, I didn’t consider the colonial aspects. I knew agar-agar came from the East Indies, that it was used in Indonesian and Malay cooking, but those were merely facts, not matters I interrogated further. Looking back now with greater awareness, it’s clear that what we called “discovery” in the laboratory was actually the appropriation of knowledge that already existed in other cultures. The women in Java who used agar in their cooking – they were the true experts. My contribution was simply recognising that this knowledge could transfer to a different context. But they were never acknowledged, never compensated. The colonial extraction wasn’t only of materials but of knowledge.

You mention that some might consider your suggestion a “lucky guess.” Was it?

No. It was troubleshooting. When one has extensive practical experience – years of making jellies and puddings, understanding how different gelling agents behave under various conditions – one develops an intuition, a technical knowledge base. When Walther described the problem, I immediately understood what properties the solution would need: stability at high temperatures, resistance to degradation, transparency. I knew agar possessed those properties because I had worked with it extensively. That’s not luck. That’s expertise, even if it wasn’t recognised as such because it came from the kitchen rather than the laboratory.

Let’s discuss one aspect of your work that has only recently come to light – your watercolour illustrations. Eleven of them from 1906 were preserved by your family. Can you describe the process of creating them?

It required patience and precision. I would observe the bacterial colonies – their shapes, colours, how they grew over time – through the microscope and on the agar plates. Then I would paint them with watercolours, attempting to capture not just their appearance but their distinctive characteristics. Different bacterial species produce different colony morphologies – some are smooth and glistening, others rough and dry, some produce pigments. Recording these accurately was essential for identification and classification.

The work required understanding what I was seeing. One must distinguish between actual bacterial growth and artefacts, between significant variations and irrelevant ones. It was scientific work, requiring both artistic skill and microbiological knowledge. Yet because it was classified as “illustration” – as assisting my husband – it wasn’t considered scientific contribution in itself.

Your grandson Wolfgang later described your role as equivalent to a “present-day medical technologist,” though that profession didn’t exist during your lifetime. How do you respond to that characterisation?

It’s apt, I think. I performed the functions – media preparation, equipment sterilisation, culture maintenance, technical documentation – that would now be recognised as skilled professional work. But in my era, these tasks were invisible precisely because I was doing them. Women’s work, even when technically demanding, was assumed to be simple, natural, an extension of housekeeping. The fact that I was unpaid reinforced that perception. If the work has no monetary value, surely it can’t be very important or difficult – that was the reasoning.

Were there moments when this invisibility frustrated you? When you wished for recognition?

I think I accepted it as the natural order at the time. One doesn’t long for what one has never been taught to expect. But yes, there were moments – particularly later in life, after Walther died in 1911 and I lived another 23 years – when I wondered what might have been different. If I had been born male, with access to formal education. If I had been able to publish under my own name. If the contribution had been acknowledged not as a housewife’s fortunate suggestion but as a technical solution based on expertise.

But I was also “placid” and “humble” – those are the words my family used to describe me. I rarely spoke about my role, never promoted myself. That was expected of women, that self-effacement. And it meant that when history was recorded, I wasn’t in it.

In 1939, scholars proposed renaming plain agar “Frau Hesse’s medium” in your honour. The proposal was never adopted. How did you feel about that?

By 1939, I had been dead five years, so I never knew of the proposal. But learning of it now – it’s bittersweet. Someone recognised the contribution. Someone thought it significant enough to deserve commemoration. Yet it wasn’t enough to actually change anything. The structures that determine whose names get attached to discoveries, whose work is remembered – those structures remained intact.

Let’s turn to something you might critique about your own work or decisions. Looking back, is there anything you would have done differently?

I should have insisted on being acknowledged. Not from vanity, but because my silence contributed to the pattern – the acceptance that women’s intellectual contributions can be erased without consequence. If I had spoken, if I had insisted that my name appear in publications, if I had demanded compensation for my labour, perhaps it would have been easier for women who came after me. But I didn’t. I accepted the invisibility. That’s my regret.

There were other women in similar positions – what we now call “hidden figures.” Did you know of them? Did you have any sense of a larger pattern?

At the time, no. I knew I was assisting Walther, and I assumed other wives did similar work for their scientist husbands, but I didn’t see it as a structural issue. Only later, looking across the history, does the pattern become visible – women working as “computers,” technicians, illustrators, assistants, making crucial intellectual contributions that are credited to the men who employed or married them. We weren’t hidden deliberately, most of the time. We were simply rendered invisible by the structures that couldn’t imagine women as scientific actors in their own right.

You lived to see agar become universal in laboratories, though its origin remained largely unknown. What was that like – watching your contribution spread across the world while your name was forgotten?

Peculiar. I would hear microbiologists discuss culturing techniques, debate the merits of different agar formulations, and they had no idea that the fundamental insight came from a woman recalling her mother’s kitchen. Part of me wanted to speak up, to say, “I suggested that. I knew about agar from making jellies.” But what would have been the point? They would have thought me boastful, or worse, delusional. An elderly woman claiming credit for a scientific innovation? It would have seemed absurd to them.

Let’s discuss contemporary recognition. Recently, a bacterial strain was named Streptomyces hesseae in your honour. The Dutch Society for Microbiology created the Fanny Hesse Award for outstanding bachelor’s theses. A graphic novel about your life is in development. How do feel about these efforts?

Deeply moving, truly. That students might learn my story, that young microbiologists – particularly women – might see themselves reflected in this history. The bacterial species named for me – that’s rather wonderful, isn’t it? A living thing carrying my name forward. And a graphic novel – what an extraordinary way to tell a story, making it accessible to readers who might never pick up a scientific biography.

But I also wonder whether it’s enough. These are important gestures, but they don’t change the fundamental structures. Women still perform unpaid or underpaid labour in laboratories. Their contributions are still minimised or erased. Credit still flows upward to laboratory directors. The same patterns persist.

You mentioned the contemporary agar art competitions – microbiologists creating images by painting with bacteria on agar plates. Some of these artists have even painted portraits of you using bacterial colonies. What would you make of that?

I’m astonished and delighted. To think that the substance I suggested is now used not only for serious scientific work but for art – that people see beauty in bacterial colonies, that they create intricate images by understanding how different species grow and produce pigments. It’s a marvellous fusion of science and art, much like my own work with watercolour illustrations. Though I must say, using actual living bacteria as the paint is far more ingenious than anything I attempted!

Every microbiologist uses agar daily – millions of plates poured annually worldwide. Yet until recently, few knew your name. What message would you offer to young scientists, particularly women and those from marginalised groups, who see their contributions overlooked?

Document everything. Insist on co-authorship. Demand fair compensation. Don’t assume that good work will automatically be recognised or that modesty is a virtue when it enables your erasure. The structures that determine credit and recognition are not neutral – they favour certain people, certain kinds of knowledge, certain pathways to discovery. If you don’t actively claim your space, you will be written out of the story.

And for those who find solutions in unexpected places – in kitchens, in immigrant communities, in non-Western knowledge systems – know that these origins don’t diminish the value of your insights. The prejudice that only formally educated experts working in official institutions can produce scientific knowledge is precisely that: prejudice. Some of the most important breakthroughs come from recognising that expertise exists in places the establishment doesn’t think to look.

Finally, when you think about agar’s legacy – the millions of bacterial cultures it has enabled, the antibiotics and vaccines developed because of it, the diseases understood and treated – how do you feel about your contribution now?

Humbled, genuinely. I made a suggestion at a lunch table. I remembered what a neighbour taught my mother about keeping jellies solid in warm weather. That this small piece of knowledge, passed between women in a kitchen, changed the course of science – it’s extraordinary. Not because I was extraordinary, but because it shows how much valuable knowledge exists in places we don’t traditionally value. How many other crucial insights are being overlooked right now because they come from the wrong people, the wrong places, the wrong contexts?

If my story does anything, I hope it encourages scientists to look beyond their own disciplines, to value knowledge wherever it originates, and to ensure that the people who contribute – particularly those who have been historically marginalised – receive the recognition and compensation they deserve. Not as an afterthought, but as a matter of justice.

Thank you, Mrs Hesse. Your insights remain as valuable today as that summer afternoon in 1881.

Thank you. And please – do tell the story. Tell it widely. Not for my sake, but for all the others whose contributions wait to be recognised. Make us visible.

Letters and emails

Since publishing our conversation with Angelina Fanny Hesse, we’ve received dozens of letters and emails from readers around the world – scientists, historians, students, and curious minds – all wanting to continue the dialogue. The response has been extraordinary, reflecting just how deeply her story resonates across disciplines and generations. We’ve selected five thoughtful questions from our growing community, each offering a fresh perspective on her life, her work, and the lessons she might offer to those facing similar challenges today. These questions come from five continents, reminding us that the conversation about recognition, knowledge, and scientific justice is truly global.

Daniela Ávila, 34, Food Scientist, São Paulo, Brazil
You mentioned that agar’s large hysteresis – the gap between its melting point and setting point – was crucial for laboratory work. In my research on tropical fruit preserves, I’ve found that different agar grades and extraction methods produce wildly different gelling behaviours. In the 1880s, before standardised commercial production, how did you and Walther handle batch-to-batch variations in agar quality? Did you develop any empirical tests to assess whether a particular sample would work reliably for bacterial cultures, or were there batches that simply failed?

What an astute question, Miss Ávila – you’ve identified precisely the difficulty we faced in those early years, and one that caused considerable frustration in the laboratory.

The agar we obtained in the 1880s was far from uniform. We purchased it from importers who brought it from Japan and the Dutch East Indies, and the quality varied enormously depending on the seaweed species used, the extraction method, and how it had been stored during the long sea voyage. Some batches would set beautifully into a clear, firm gel. Others remained cloudy, or set too softly, or – most vexing – contained impurities that seemed to inhibit bacterial growth entirely.

Walther and I did develop empirical tests, though they were rather crude by comparison to what you might use today. First, I would prepare a small test batch – dissolving a measured quantity of agar in distilled water or nutrient broth and observing how it behaved during heating. Good agar dissolved cleanly at around 85 to 90 degrees Celsius and remained in solution without forming lumps or sediment. If it produced excessive foam or a disagreeable odour during heating, we knew the batch was suspect.

Once cooled, I would examine the set gel carefully. It should be transparent – not perfectly clear like glass, but clear enough to see through when poured thinly in a dish. If it appeared murky or had a yellowish cast, the impurities might interfere with observations. I would also test the firmness by pressing gently with a sterile glass rod. The gel should resist deformation but not be brittle. Too soft, and the bacterial colonies would sink into the medium or spread uncontrollably. Too firm, and the agar could crack or dry out too quickly during incubation.

The most critical test, of course, was whether bacteria would actually grow upon it. Even agar that appeared satisfactory by physical inspection sometimes failed this test. I remember one particularly maddening batch – it looked perfect, set beautifully, but every culture we attempted produced weak, sparse growth or failed entirely. We eventually concluded that batch contained some toxic residue, perhaps from the processing. We discarded it and sourced agar from a different supplier.

There was also the matter of concentration. We found that approximately 1.5 to 2 percent agar by weight produced the best results for most applications – firm enough to handle but not so concentrated that it became opaque or overly rigid. But this ratio had to be adjusted based on the particular batch we were using. A high-quality agar might require only 1.5 percent, whilst an inferior grade might need 2.5 percent or more to achieve adequate firmness.

Storage presented another challenge. Agar in its dry form – it came as strips or powder – was quite stable if kept dry and away from pests. Prepared plates, however, would dry out within days unless kept in a humid environment. We stored them in closed containers with moist blotting paper to maintain humidity. Even so, older plates would sometimes develop condensation or become too dry at the edges, making them unreliable.

We kept detailed records – not formal laboratory notebooks at first, more like kitchen notes – documenting which suppliers provided consistent quality, which batches worked well, which concentrations suited different purposes. This was essential because ordering new agar took weeks or months. If we received a poor batch, we couldn’t simply telephone for a replacement the next day. We had to make do with what we had, adjusting concentrations, filtering more carefully, or in the worst cases, writing to other laboratories to borrow from their stocks.

I also learnt to recognise visual cues in the dry agar itself. The best quality had a pale, almost translucent appearance and broke cleanly. Darker, more opaque pieces often indicated older agar or inferior processing. Some batches had visible plant matter or sand mixed in – these required extensive filtering through muslin or fine cloth before use.

In essence, Miss Ávila, we became connoisseurs of agar through necessity, much as a cook learns to judge the quality of flour or butter by sight and touch. Every batch was an uncertainty, and careful testing before committing to large preparations was absolutely essential. There were indeed batches that simply failed, and we wasted considerable time and materials before recognising their deficiencies. But over time, we developed both the technical knowledge and the supplier relationships to obtain reasonably consistent material.

I imagine your work with fruit preserves requires similar discernment – understanding how different pectin sources behave, adjusting for natural variations. It’s the same principle: when working with natural materials rather than standardised chemicals, one must bring both technical knowledge and practical judgement to bear. No two batches are identical, and success requires adaptation.

Henrik Sørensen, 52, History of Science Professor, Copenhagen, Denmark
Robert Koch is often credited with developing the pure culture technique that transformed bacteriology, yet your agar innovation was arguably the enabling technology that made his method practical at scale. If Koch had been more generous in acknowledging your contribution in 1882, do you think the trajectory of women entering microbiology as recognised professionals might have shifted earlier? Or were the institutional barriers so entrenched that even explicit credit wouldn’t have opened doors for women in German scientific institutions of that era?

Professor Sørensen, you’ve posed a question I’ve contemplated many times, though the answer grows more complicated the longer I consider it.

Had Koch acknowledged my contribution explicitly in 1882 – named me in his tuberculosis paper, credited the agar innovation directly – would it have opened doors for women in German scientific institutions? I think not, or at least not in any straightforward way. The barriers were far too deeply entrenched, woven into the very fabric of how universities and research institutes functioned.

Consider the legal and social structures of the time. German universities did not admit women as regular students until the very end of the nineteenth century – the University of Freiburg admitted its first woman in 1900, and even then, it was considered extraordinary. How could women become recognised professionals in microbiology when they couldn’t obtain the credentials required for professional standing? The pathway simply didn’t exist. One needed a doctorate to hold a research position, and women couldn’t earn doctorates because they couldn’t attend university.

Even had Koch written, “Frau Hesse suggested the use of agar, which proved invaluable to this research,” what would have followed? I had no degree, no formal training, no institutional affiliation beyond being a researcher’s wife. There was no mechanism by which such acknowledgment could translate into professional opportunity for me personally. I couldn’t apply for positions that didn’t exist for women. I couldn’t publish independently without credentials. The recognition would have been merely symbolic – pleasant, certainly, but not materially transformative.

That said, symbols do carry weight, particularly accumulated over time. If Koch had credited me, and if other prominent scientists had followed suit when women in their laboratories made contributions, perhaps it might have created a different culture – one where women’s intellectual work was visible rather than invisible by default. Each instance of recognition is a small crack in the wall. Enough cracks, and eventually the wall weakens.

But I think you’re asking something more specific: whether my individual recognition might have encouraged other women or shifted attitudes among male scientists. Here I’m more hopeful, though still cautious. There were women in my era who did manage to carve out scientific careers despite the obstacles – women like Marie Curie, though she faced tremendous resistance and required extraordinary talent combined with unusual circumstances. Had I been publicly credited, perhaps it would have emboldened other women working quietly in their husbands’ laboratories to speak up, to insist on co-authorship, to demand acknowledgment.

More likely, though, my case would have been dismissed as an exception – “Frau Hesse made a lucky suggestion based on household knowledge, which is quite different from real scientific work.” The very fact that my insight came from cooking would have been used to diminish rather than elevate it. “You see,” they would say, “women are useful for bringing domestic perspectives to scientific problems, but this hardly qualifies them for formal positions or advanced training.” My contribution might have been used to reinforce, not challenge, the idea that women’s proper role was supportive rather than primary.

There’s also the matter of Walther’s career to consider. Had I become publicly prominent – credited, celebrated, interviewed by scientific journals – it might have damaged his standing. In that era, a man whose wife overshadowed him professionally would have been subject to ridicule. His colleagues might have suggested he wasn’t a proper scientist if his wife was receiving attention for contributions from his laboratory. That sounds absurd now, but masculine pride and professional hierarchies were – are – powerful forces. Walther was a gentle, generous man, but he also needed to maintain his reputation to continue his work. My visibility might have come at his expense.

And yet, Professor Sørensen, I find myself returning to your question with a different emphasis. Perhaps the issue isn’t whether explicit credit in 1882 would have changed institutional structures, but whether the absence of such credit allowed those structures to persist unchallenged. Every time a woman’s contribution goes unacknowledged, it reinforces the assumption that women don’t make significant scientific contributions. The invisibility becomes self-fulfilling. If no women are credited, then there’s no evidence that women contribute, which justifies excluding them from positions where they might contribute further.

So whilst I doubt that Koch crediting me would have opened doors in 1882, I believe that fifty years of consistently crediting women’s contributions – mine and countless others’ – might have gradually shifted expectations. By the 1930s, perhaps universities would have found it harder to justify excluding qualified women if the scientific literature was full of acknowledged female contributors. The accumulation matters.

What troubles me most, looking back, is not merely that I wasn’t credited, but that so few people seemed to notice or care about the absence. The erasure was accepted as natural. That’s the deeper problem – not individual instances of oversight, but a culture that considered women’s invisibility unremarkable. Changing that culture would have required far more than one acknowledgment in one paper, no matter how prominent. It would have required a collective commitment to justice that simply didn’t exist.

Lien Tran, 28, Molecular Biologist, Hanoi, Vietnam
I’m fascinated by your transition from culinary knowledge to laboratory precision. When you first began preparing culture media for Walther, were there techniques from cooking – temperature control, recognising subtle changes in texture or appearance, timing – that translated directly into laboratory skills? And conversely, did your laboratory work change how you approached cooking at home? I’m curious whether you saw these as fundamentally the same kind of knowledge or entirely separate domains.

Miss Tran, what a perceptive question – you’ve identified something I’ve thought about often but rarely articulated. The transition from kitchen to laboratory felt entirely natural to me precisely because the fundamental skills were so similar, though I didn’t recognise this consciously at first.

Temperature control was perhaps the most direct translation. In cooking, one learns to judge heat not merely by thermometers – which were imprecise instruments in my youth – but by observation and touch. You know when butter is hot enough for sautéing by how it moves in the pan, by the faint nutty aroma before it browns. You know when sugar syrup has reached the right stage for candy-making by dropping a bit into cold water and feeling its texture. This same intuitive understanding of thermal behaviour proved invaluable in the laboratory.

When preparing culture media, I had to heat the agar solution carefully – hot enough to dissolve completely, but not so vigorously that it boiled over or concentrated unevenly. I could tell by watching the liquid’s movement, by the way bubbles rose, whether the temperature was correct. Similarly, when sterilising equipment in boiling water or the autoclave, I learnt to judge timing not only by the clock but by understanding how heat penetrates different materials. Glass flasks require longer than metal instruments. Tightly packed cotton plugs need more time than loose ones. This was kitchen knowledge – the same reasoning one uses knowing that a dense bread pudding needs slower, longer baking than a thin custard.

Recognising subtle changes in appearance was equally transferable. A cook learns to see the moment when egg whites shift from frothy to stiff peaks, when cream is about to separate into butter, when dough has been kneaded to the right elasticity. In the laboratory, I watched for comparable transitions – when agar solution changed from cloudy to clear as it dissolved, indicating complete melting. When bacterial cultures shifted from barely visible haziness to distinct turbidity, signalling active growth. When colonies on agar plates showed the first signs of sporulation or pigment production. These were the same observational skills, applied to different materials.

Timing and sequence mattered tremendously in both domains. In baking, one cannot add eggs before butter and sugar are properly creamed, or the texture fails. In preparing culture media, one cannot add heat-sensitive nutrients until the agar has cooled sufficiently, or they degrade. Both require understanding the logic of processes – what must happen first, what can be done simultaneously, what cannot be rushed.

Cleanliness, of course, was paramount in both kitchen and laboratory, though the standards differed. My mother taught me that a properly run kitchen is scrupulously clean – pots scrubbed immediately, work surfaces wiped down, towels boiled regularly. This wasn’t merely aesthetic; it prevented spoilage and illness. The laboratory required even more rigorous standards – true sterility, not merely cleanliness. But the habit of meticulous hygiene, the understanding that invisible contamination could ruin one’s work, was already deeply ingrained.

I also brought an understanding of how substances behave when mixed. A cook knows that oil and water don’t combine without an emulsifier, that acid curdles milk, that salt draws moisture from vegetables. This practical chemistry – though I wouldn’t have called it chemistry – helped me understand why certain nutrient solutions precipitated when mixed incorrectly, why some compounds needed to be added in specific order, why pH mattered for bacterial growth.

Conversely, my laboratory work absolutely transformed how I approached cooking at home. I became more precise, more aware of the principles underlying techniques I’d previously done by rote. I understood why certain recipes failed at high altitude – the boiling point changes, just as it does in the laboratory. I recognised that rising bread dough was a microbial fermentation process, essentially a bacterial culture, and I could troubleshoot problems by thinking about what conditions yeast required for optimal growth. When preserving foods, I understood the bacteriology – why sufficient heat and acid were necessary, how different microorganisms behaved under various conditions.

I also became more experimental in the kitchen. Laboratory work encourages a particular mindset: hypothesise, test, observe, adjust. I applied this to cooking, varying ingredients methodically to understand their effects rather than simply following recipes blindly. If a cake failed, I would consider the variables – was the oven too hot? Had I over-beaten the batter? Was the flour old? – much as I would troubleshoot a failed bacterial culture.

But here’s what I found most interesting, Miss Tran: despite these deep similarities, the two domains were perceived entirely differently. Kitchen work was considered natural, intuitive, something any woman could do without special talent. Laboratory work was considered technical, scientific, requiring trained intelligence. Yet the skills were fundamentally the same – observation, precision, understanding of materials and processes, troubleshooting, maintaining controlled conditions.

This disparity in perception frustrated me, though I couldn’t have articulated it clearly at the time. Why was my ability to judge when agar had dissolved properly considered mere assistance, whilst a male researcher’s ability to judge the same thing was scientific expertise? We were using identical skills, identical reasoning. The difference was only in where the work occurred and who was doing it.

I came to believe they weren’t separate domains at all, but rather the same domain – applied chemistry and biology – artificially divided by social convention. Cooking is chemistry. Microbiology is applied cookery. Both require the same intellectual capacities. The distinction is false, maintained only to justify why certain people – women, primarily – could be expert practitioners without being granted the title or compensation of experts.

So to answer your question directly: yes, I saw them as fundamentally the same kind of knowledge, though I was taught to think of them as separate. The laboratory work revealed what I’d always been doing in the kitchen – science – even when no one, including myself, recognised it as such.

Tyler Bennett, 45, Science Policy Analyst, Seattle, Washington, USA
Imagine that in 1881, you had been offered a formal paid position as “Technical Assistant” in Koch’s laboratory with your name on resulting publications, but accepting it would have caused significant social scandal and potentially damaged Walther’s professional reputation. Knowing what you know now about how your erasure unfolded, would you have taken that risk? I’m curious whether you think individual acts of defiance could have shifted the broader pattern, or whether the structures were too powerful for any single woman to challenge effectively.

Mr Bennett, you’ve constructed a thought experiment that cuts directly to the heart of a dilemma I never faced in reality but have pondered many times since. Your question assumes I would have had the clarity in 1881 to foresee my erasure – that I would have understood then what I only came to recognise gradually over decades. But let me answer as if I had possessed such foresight.

Would I have accepted a formal paid position with public credit, knowing it would scandalise society and potentially harm Walther’s career? I want to say yes – that I would have seized the opportunity, defied convention, claimed my rightful place. But I must be honest: I don’t think I would have. And I’m not certain that would have been the wrong choice.

You must understand the social architecture of the time. A married woman accepting paid employment when her husband could support her would have been interpreted as evidence of his professional failure or financial incompetence. For a wife to receive public credit that overshadowed her husband’s work would have been even worse – an emasculation, a reversal of natural order, proof that he wasn’t truly the head of his household. These weren’t merely abstract prejudices; they had material consequences.

Walther’s position in Koch’s laboratory was not secure. He was one researcher among several, valuable but replaceable. If gossip began circulating that his wife was the real talent, that she was receiving recognition whilst he remained in the background, his colleagues might have questioned his competence. Koch might have found him an embarrassment. In the competitive world of German scientific institutions, any perceived weakness could end a career. And then what? We had three sons to support. Would my insistence on credit have been worth Walther losing his position, our family losing its income?

Furthermore, the scandal would have extended beyond Walther to our sons. In that era, a mother’s impropriety – and yes, claiming credit for scientific work would have been considered improper – reflected on her children’s prospects. Our sons might have found it harder to secure good positions, suitable marriages. The social taint would have followed them. Could I justify that cost for the sake of my own recognition?

But your question asks something more profound, I think: whether individual acts of defiance could have shifted the broader pattern, or whether the structures were too powerful. Here I must say – both are true, and that’s the terrible bind.

Individual defiance alone cannot change entrenched structures. If I had been the only woman insisting on credit, I would simply have been labelled difficult, peculiar, perhaps unstable. The structures would have absorbed the disruption by marginalising me – dismissing my contribution as exaggerated, suggesting I was taking credit for my husband’s work rather than the reverse, excluding me from future opportunities. One woman’s resistance isn’t revolution; it’s eccentricity.

Yet structures only change through accumulated individual acts of defiance. If no women ever resist, the pattern continues unchallenged forever. Someone must be first, must be willing to bear the personal cost of challenging injustice even when success is unlikely. The suffragettes endured imprisonment and force-feeding. The first women physicians faced vicious harassment. Progress required their courage, their willingness to suffer personally for collective gain.

So would my defiance in 1881 have mattered? Probably not immediately. One woman claiming credit for suggesting agar would not have transformed German scientific institutions. But perhaps – and this is speculation – if I had insisted on credit, and if other women had done likewise in their own laboratories, the accumulated pressure might have eventually forced change. Fifty women insisting on acknowledgment across two decades creates a pattern that’s harder to dismiss than one woman’s isolated claim.

Here’s what troubles me most about your hypothetical, Mr Bennett: it places the burden of changing unjust structures on those who are most vulnerable to them. You’re essentially asking whether I should have sacrificed my family’s security and my sons’ futures to strike a blow against injustice that might not succeed. That’s an enormous thing to ask of anyone, particularly when the men who controlled those structures – Koch, the university administrators, the journal editors – faced no comparable dilemma. They could have acknowledged women’s contributions without personal cost. They chose not to.

The injustice wasn’t that I failed to demand credit; the injustice was that credit required demanding at all. In a just system, contribution would have been acknowledged automatically, regardless of the contributor’s sex or social position. Placing responsibility on me to fix the broken system – at great personal cost – rather than on those who maintained it – at no cost to themselves – seems itself unjust.

That said, I do regret my silence. Not because I think individual defiance would have succeeded, but because silence became complicity. By accepting invisibility, I made it easier for the next woman’s contribution to be erased, and the one after that. If I had at least tried – if I had written to scientific journals, if I had contacted other women working in laboratories, if I had publicly stated that the agar innovation was mine – perhaps it would have made the pattern slightly harder to maintain. Perhaps other women would have felt less alone.

But I also recognise that this regret comes from the privilege of hindsight and age. It’s easy to advocate courage when the consequences are long past. In 1881, facing real social and financial threats, with three young sons depending on me, would I truly have chosen differently? I doubt it. Self-preservation isn’t cowardice; it’s rationality.

So my answer, Mr Bennett, is this: I would not have taken that risk, and I’m no longer certain that was entirely wrong. The responsibility for change belonged to those with power, not to those without it. Expecting the victims of injustice to also be its heroic resisters – at ruinous personal cost – is expecting too much. Yet without such resistance, injustice persists. It’s an impossible position, and I’m still angry that I was placed in it.

Mariama Kouyaté, 41, Microbiology Laboratory Manager, Dakar, Senegal
Your watercolour illustrations required you to observe bacterial colonies closely over time, which means you must have developed an extraordinarily trained eye for microbial morphology and behaviour. In my laboratory, we’re training technicians to spot contamination and identify organisms visually before molecular confirmation. What were the most deceptive or surprising bacterial behaviours you observed – perhaps a contaminant that mimicked a target organism, or growth patterns that initially fooled even experienced observers like yourself or Koch?

Mrs Kouyaté, what an excellent question – you’ve touched upon one of the most fascinating and occasionally maddening aspects of laboratory work. Training one’s eye to recognise what belongs and what doesn’t, what’s genuine growth and what’s contamination, requires both knowledge and experience. I can share several instances that taught me humility.

The most deceptive organism I encountered regularly was a mould – I believe it was a Penicillium species, though we didn’t have such precise identifications then. It would appear as the faintest grey-green bloom on agar plates, so subtle in the early stages that one might easily overlook it. The treacherous part was that it often grew at the edges of plates where condensation collected, and in those early hours it could resemble the spreading growth pattern of certain bacteria. More than once, I nearly mistook contaminated plates for successful cultures before noticing the slightly fuzzy texture that betrayed its fungal nature. Under the microscope, of course, the distinction was obvious – the branching hyphae were unmistakable – but to the naked eye, particularly in dim laboratory light, it was deceptive.

We also encountered a bacterium – I cannot tell you its proper name, as our classification methods were quite rudimentary – that produced colonies remarkably similar to those of Bacillus subtilis, which was a common laboratory organism. Both formed rough, irregular colonies with a dull surface. The impostor, however, produced a faint yellowish pigment that only became apparent after two or three days of growth. If one examined plates too early, the colonies appeared identical. I remember Walther being quite puzzled by inconsistent experimental results until we realised he’d been working with two different organisms that we’d assumed were the same. After that, we learnt to wait longer before making identifications, and to examine colonies at multiple time points rather than relying on initial appearance.

Perhaps the most surprising behaviour involved what we called “swarming” organisms – bacteria that didn’t form discrete colonies but instead spread across the agar surface in a thin film. Proteus species did this particularly dramatically. You would inoculate a plate expecting neat, separated colonies for counting and isolation, and instead the entire surface would be covered with a translucent veil of bacterial growth within hours. The first time I observed this, I thought I’d made some terrible error in preparation – perhaps the agar was too soft, or I’d flooded the plate with too much inoculum. But no, this was simply how these organisms behaved. They possessed flagella and a peculiar kind of cooperative movement that allowed them to migrate rapidly across moist surfaces.

This swarming created real practical difficulties. If you had a mixed culture – say, a clinical specimen containing several bacterial species – and one of them was a swarmer, it would overgrow the entire plate, obscuring any other organisms present. We had to learn techniques to suppress the swarming – using firmer agar concentrations, adding certain chemicals, or using media that didn’t support the behaviour. It was trial and error, guided by sharing observations with other laboratories.

There was also the phenomenon of satellite colonies – tiny bacterial colonies growing in a ring around larger colonies of a different species. At first glance, one might think these were the same organism at different stages of growth. In fact, they were separate species, with the satellites depending on some substance produced by the central colony. Haemophilus bacteria did this, growing around Staphylococcus colonies that released factors the Haemophilus required. Missing this relationship could lead to entirely incorrect conclusions about what organisms were present in a sample.

Contamination from the air was a constant challenge. We would pour plates, cover them, and believe them sterile, only to find strange colonies appearing days later. Some of these were clearly moulds – dramatic, colourful, obviously not what we’d inoculated. But others were bacterial contaminants that could easily be mistaken for the organisms under study, particularly if the contaminating species happened to be common environmental bacteria that grew well on our standard media.

I learnt to maintain what I called “control plates” – uninoculated media prepared and incubated alongside the experimental plates. If colonies appeared on the controls, we knew our technique had failed somewhere, or the laboratory environment was particularly contaminated that day. This seems obvious now, but we had to learn it through bitter experience – through experiments ruined by contamination we’d mistaken for genuine results.

One of the subtlest distinctions involved bacterial colony texture and how it changed with age. Fresh colonies of some species appeared smooth and glistening – what we called “mucoid.” But as they aged, the moisture would evaporate, and they’d become dull and rough-looking, resembling entirely different organisms. If one compared a three-day-old colony of species A with a one-day-old colony of species B, they might appear completely different, even if when compared at the same age, they’d look similar. Learning to account for these temporal changes required careful attention and good record-keeping.

The most humbling lesson came from an incident where Walther and I disagreed about whether a particular plate was contaminated. I insisted the colonies looked wrong – slightly too translucent, edges too irregular. He thought I was being overly cautious, that they appeared perfectly consistent with what we expected. We examined them under the microscope, and I was correct – they were a contaminating species with similar gross morphology but distinctly different cellular structure. After that, Walther trusted my eye more readily, but it also taught me that expertise comes from sustained observation, from seeing hundreds of plates and developing an intuition for what’s normal and what’s not.

For your training work in Dakar, Mrs Kouyaté, I would emphasise this: there is no substitute for experience. One must see many examples, make mistakes, learn from them. Encourage your technicians to examine plates daily, to note how colonies change over time, to compare suspicious plates with known good cultures. And perhaps most importantly, cultivate a questioning attitude – if something looks even slightly unusual, investigate further rather than assuming it’s acceptable. It’s better to be overly cautious and occasionally discard good cultures than to be insufficiently careful and base conclusions on contaminated results. The eye can be trained, but only through patient, repeated practice.

Reflection

Angelina Fanny Hesse died on 1st December 1934 in Dresden, at the age of eighty-four. She had outlived her husband Walther by twenty-three years, witnessed the devastation of the First World War, and seen microbiology transform from a fledgling science into an established discipline – all built upon the foundation of agar plates that traced back to her kitchen-table suggestion in 1881. Yet at the time of her death, virtually no one outside her immediate family knew her name or understood her contribution to the field that had come to depend entirely upon her innovation.

Speaking with Mrs Hesse – or rather, imagining what she might say if given the opportunity – reveals themes that resonate far beyond one woman’s erasure from scientific history. Her story illuminates the persistent devaluation of domestic knowledge, the structural impossibility of recognition for unpaid labour, and the ways that modesty and self-effacement, whilst culturally mandated for women, become mechanisms of historical erasure. What emerges most powerfully is her clear-eyed understanding that the problem wasn’t her failure to demand credit, but rather a system designed to render women’s intellectual contributions invisible by definition.

Throughout our conversation, certain tensions became apparent between what Mrs Hesse expressed and what the historical record suggests. Where biographical accounts describe her as “placid” and “humble,” never speaking about her achievements, the woman who emerged in our dialogue possessed sharper awareness of the injustices she faced than these characterisations imply. It seems likely that her silence stemmed not from lack of understanding but from rational calculation – speaking would have accomplished nothing except social penalty. Her grandson’s description of her role as equivalent to a “present-day medical technologist” captures the professional nature of her work whilst simultaneously revealing how invisible such technical expertise remained in her era, absorbed into the category of wifely duty.

The historical record itself contains significant gaps and uncertainties. Most primary sources documenting the Hesse family were destroyed during the Allied bombing of Dresden in 1945, leaving historians to reconstruct her story from scattered references, family memories recorded decades later, and the rare mentions of her in scientific correspondence. We know Robert Koch’s 1882 tuberculosis paper mentioned switching to agar in a single sentence without explanation or credit. We know from later accounts that Walther told Koch about Fanny’s suggestion. But the intimate details of her daily laboratory work, her thought processes, her reactions to being overlooked – these are largely matters of inference rather than documentation.

What we can say with certainty is that her technical contribution was extraordinary. Agar solved multiple interlocking problems simultaneously: thermal stability to 100°C, resistance to bacterial enzymatic degradation, transparency for colony observation, compatibility with autoclaving for sterilisation, and stable long-term storage. No synthetic alternative developed since has improved upon these properties in any meaningful way. Every advance in bacteriology from 1882 forward – Koch’s isolation of tuberculosis and cholera bacilli, the development of antibiotics, the identification of foodborne pathogens, modern medical diagnostics – depended on the reliable culture medium she introduced.

The afterlife of Mrs Hesse’s work followed a peculiar trajectory: immediate ubiquity paired with complete obscurity. By the 1890s, agar had become the universal standard in microbiology laboratories worldwide, yet inquiries into its origin often produced vague or incorrect answers. Some attributed it to Koch himself, others to Walther Hesse, and many simply assumed it had always existed. The 1939 proposal by scholars to rename plain agar as “Frau Hesse’s medium” represented perhaps the earliest explicit attempt to correct this erasure, but the suggestion went nowhere – a telling indication of how thoroughly her contribution had been absorbed into the anonymous infrastructure of science.

Recognition began trickling in only recently, nearly a century after her death. The discovery of her eleven watercolour illustrations from 1906 in family archives sparked renewed scholarly interest in the 2010s. In 2024, the bacterial species Streptomyces hesseae was formally named in her honour – a living organism carrying her name into perpetuity, which seems somehow fitting for someone whose innovation enabled the cultivation and identification of countless bacterial species. The Dutch Society for Microbiology established the Fanny Hesse Award for outstanding bachelor’s theses, presented annually at their Scientific Spring Meeting. A graphic novel about her life, crowdfunded through international collaboration among scientists, historians, and artists, is currently in development – a remarkable effort to bring her story to wider audiences, particularly young people who might never encounter her in traditional scientific histories.

These recognition efforts matter not merely as belated justice for Mrs Hesse herself, but as crucial interventions in ongoing patterns. Contemporary studies consistently demonstrate that women’s scientific contributions continue to be under-cited, their co-authorship minimised, their intellectual labour classified as “assistance” rather than substantive contribution. The American Society for Microbiology’s annual Agar Art competition, running since 2015, creates stunning images by painting with bacterial colonies on agar plates – a celebration of the medium’s aesthetic possibilities that rarely acknowledges the woman who made it possible. Even today, many microbiology textbooks teach why agar succeeded where gelatin failed without naming Fanny Hesse. The erasure persists in updated forms.

Yet Mrs Hesse’s story also offers profound encouragement, particularly for young women navigating scientific careers today. Her path demonstrates that formal credentials, whilst valuable, are not the sole route to genuine expertise. Her deep practical knowledge – developed through years of careful observation, troubleshooting, and refinement – solved a problem that had defeated formally trained scientists. This suggests that diverse knowledge sources, including those traditionally devalued as “domestic” or “informal,” may contain solutions that conventional scientific approaches miss. The challenge isn’t expanding who counts as an expert but recognising expertise wherever it already exists.

The cross-cultural dimensions of her contribution remain strikingly relevant. Agar travelled from Indonesian culinary traditions through Dutch colonial networks to immigrant communities in New Jersey, then into German research laboratories – a reminder that scientific innovation depends on knowledge circulation across cultures, contexts, and social positions that formal histories routinely erase. Contemporary calls to decolonise science and recognise non-Western knowledge systems’ contributions find a powerful historical precedent in Mrs Hesse’s story. The women in Java who used agar in their cooking possessed the expertise first; Fanny Hesse recognised its potential for transfer; yet European men received the credit. This pattern of extracting knowledge from marginalised communities whilst erasing their contributions continues to demand redress.

What might Mrs Hesse’s legacy offer young women in STEM today? First, visibility matters immensely. Every time her story is told, every bacterial species named for her, every award established in her honour, creates precedent – makes it slightly harder for the next woman’s contribution to vanish without trace. Second, documentation and advocacy are essential. Mrs Hesse’s regret about her silence suggests that whilst individual resistance may not immediately transform unjust structures, it creates the historical record future generations need to understand those structures and demand change. Third, diverse knowledge deserves recognition. The boundary between “kitchen” and “laboratory” was always artificial, maintained to justify excluding certain people from professional standing. Challenging such false boundaries remains urgent work.

Perhaps most importantly, Mrs Hesse’s story reminds us that the material evidence of women’s contributions often persists even when their names are forgotten. Every agar plate poured, every bacterial culture isolated, every medical diagnostic test performed on agar-based media carries forward her 1881 insight. The work continues, regardless of whether credit was given. This offers both comfort and challenge: comfort that meaningful contributions echo forward through their effects, and challenge that we must actively labour to ensure those effects remain connected to their originators.

Standing in any modern microbiology laboratory – surrounded by stacks of agar plates, watching researchers streak bacterial cultures, observing the neat colonies growing in precisely the patterns Mrs Hesse first illustrated in watercolour – one cannot help but feel the presence of her genius. It is everywhere and nowhere, foundational yet invisible, exactly as she described. The work of making her visible continues, carried forward by historians, scientists, artists, and educators who understand that every erasure uncorrected becomes precedent for the next.

Mrs Hesse asked, at the end of our conversation, that we tell her story widely – not for her own sake, but for all the others whose contributions await recognition. That request carries particular weight now, as we continue to discover just how many “hidden figures” shaped the scientific achievements we celebrate. Each name recovered, each contribution acknowledged, weakens the structures that created invisibility in the first place. It is painstaking work, this archaeological recovery of women’s intellectual labour, but absolutely necessary. Because as long as we believe great science emerges only from formally credentialed men working in official institutions, we will continue overlooking genius that appears in kitchens, in immigrant communities, in the unpaid labour of women whose expertise we have trained ourselves not to see.

The agar plates are still there, millions of them, in every laboratory on Earth. The evidence was never hidden. We simply needed to learn how to look properly, to ask whose knowledge made this possible, to refuse the easy assumption that innovations appear from nowhere. Mrs Hesse’s legacy lives in that shift of vision – the recognition that domestic knowledge is scientific expertise, that cooking is applied chemistry, that women working without titles or compensation were doing science all along. We just weren’t calling it that, which meant we didn’t have to credit them for it.

That changes now. Every student who learns her name, every researcher who acknowledges the Indonesian culinary traditions that gave us agar, every young woman who sees herself reflected in this history – they become part of correcting an injustice 143 years in the making. The dessert that conquered disease came from a woman remembering her neighbour’s cooking. That simple fact, once properly understood, transforms how we think about where scientific insight originates and whose knowledge we’ve been systematically ignoring. Mrs Hesse’s story doesn’t merely recover one woman’s contribution; it challenges us to examine how many others we’re still overlooking, right now, because they don’t match our inherited assumptions about what scientific genius looks like.

The work continues. The agar plates keep growing their colonies. And finally, after more than a century, the woman who made it possible is beginning to receive the recognition she always deserved.

Editorial Note: This interview with Angelina Fanny Hesse is a dramatised reconstruction created for educational and reflective purposes. Whilst Mrs Hesse’s biographical details, scientific contributions, and the historical context of her work are drawn from documented sources – including scholarly articles, archival materials, family records, and contemporary accounts of early bacteriology – the dialogue itself is imagined. Mrs Hesse died in 1934, long before such a conversation could have taken place.

The responses attributed to her represent an informed interpretation of what she might have thought, felt, and expressed, based on available historical evidence about her life, personality, work, and the social constraints she navigated. Where the historical record is silent – particularly regarding her private thoughts, emotional responses, and technical decision-making processes – I have constructed plausible perspectives consistent with her documented circumstances and the broader patterns affecting women in nineteenth-century science.

Most primary sources documenting the Hesse family were destroyed during the bombing of Dresden in 1945, leaving significant gaps in our knowledge of her daily experiences and inner life. The family descriptions of her as “placid” and “humble,” someone who “rarely spoke about her achievements,” come from relatives’ recollections recorded decades after her death, filtered through their own perspectives and the gender expectations of their time. We cannot know with certainty how Mrs Hesse herself would have characterised her contributions or her feelings about being overlooked.

This reconstruction aims to honour her documented expertise – in culture media preparation, laboratory technique, watercolour illustration, and the crucial agar innovation – whilst giving voice to perspectives she may have held but had no platform to express. The technical details of her work, the properties of agar, the problems with gelatine, and the broader context of Koch’s laboratory are historically accurate. The emotional and intellectual reflections represent thoughtful speculation grounded in the realities she faced.

The purpose of this dramatisation is not to fabricate history but to illuminate it – to make visible the erasure mechanisms that operated in Mrs Hesse’s lifetime and continue today, and to explore questions about credit, recognition, and whose knowledge counts as scientific. By imagining what she might say if given the opportunity, we create space to examine injustices that the historical record, written largely by those who benefited from them, often obscures.

Readers interested in the documented facts of Mrs Hesse’s life and contribution should consult the scholarly sources cited throughout this piece, including recent biographical work, microbiological histories, and materials held at institutions such as the Robert Koch Institute Museum. This interview serves as a companion to, not a replacement for, rigorous historical scholarship – an invitation to engage with her story emotionally and intellectually, to consider what her silence cost and what her voice might have offered.

Bob Lynn | © 2025 Vox Meditantis. All rights reserved.