Category Archives: Material History

Tales from the Archives: Of Dirty Books and Bread

As our loyal readers know, yesterday we celebrated our fifth birthday! We now have over 500 posts in our archives and over 120 pages for readers to sift through. What a wealth of knowledge on recipes from our wonderful contributors. However, with so much material on the site, it’s easy for earlier pieces to be forgotten. So, the editors have decided that, every now and then, we’ll pull something out of the archives to share with our readers anew in a ‘Tales from the Archives’ series.

This month, we’re getting a bonus Tales from the Archives. Here in the U.K., The Great British Bake Off airs on Tuesday nights and, this season, contestant Kate Lyon regularly uses historical recipes. Tonight, bread is on the menu!  This post, by Anke Timmermann, is one of my favourite bread-related posts. Let’s just say that Wonder Bread takes on a whole new meaning!

We’d also like to congratulate Anke on her new business. She left academia a couple years ago to move into the antiquarian book business and recently opened her own in London: A T Scriptorium.
Editor Lisa Smith

By Anke Timmermann

There are certain things that even the most innocent manuscript scholar cannot avoid, among them dirty books. This post will discuss the traces that careless readers have left on manuscript pages since they were first filled with writing: smudges and splodges created through physical contact between books and readers. Blemishes and damaged manuscripts have occurred to me recently in different guises as I was tracing alchemy across Cambridge manuscript collections. The following three observations may amuse and inspire the current audience – not least because they connect codices with bread, cheese and other foodstuffs.

Bad And Good Dirt

Failed attempt at book conservation in the 19th century: the opposite of cleaning (Wikimedia Commons)
Failed attempt at book conservation in the 19th century: the opposite of cleaning (Wikimedia Commons) 

Richard de Bury, cleric, bibliophile of the early fourteenth century and author of a book-lover’s guide to books, wrote passionately about the correct handling of codices. Books were meant to be seen but not touched. In the appropriately entitled Philobiblon, de Bury exemplifies readers’ common if damaging behaviour in the figure of ‘some headstrong youth’:

He does not fear to eat fruit or cheese over an open book, or carelessly to carry a cup to and from his mouth; and because he has no wallet at hand he drops into books the fragments that are left.

Many modern users of libraries observing fellow-readers will find this scenario familiar.

But in recent years scholarship has made visible previously hidden signs of historical book usage. An excellent article of 2010 demonstrates the use of a densitometer, ‘a machine that measures the darkness of a reflecting surface’, e.g. for revealing traces of medieval readers’ kisses of saints’ images.[1] One can only imagine, and deduce from obvious stains, what a similar analysis of recipe books would uncover.

Medieval Bread and Books

Image of a man feeding a dog with bread (according to the library catalogue), with unidentified stains. French manuscript of Christmas carols, early sixteenth century. Free Library of Philadelphia, MS Lewis E 211, f. 8r.
Image of a man feeding a dog with bread (according to the library catalogue), with unidentified stains. French manuscript of Christmas carols, early sixteenth century. Free Library of Philadelphia, MS Lewis E 211, f. 8r.

Dirt on book pages did not need to wait for modern technology to be noted. Late medieval book owners remarked upon and tried to find solutions for the appearance of unwanted substances on their manuscript pages. Recently discovered examples include paw prints and bodily fluids left by cats in manuscripts, but after the fact, at a stage when these manuscripts were beyond hope of cleaning.[2]

I was, therefore, delighted to find the following instruction for cleaning books in a manuscript at Cambridge University Library (CUL MS Ee.1.13, f. 141r).

ffor to make clene thy boke yf yt be defouled or squaged[3]

Take a schevyr of old broun bred of þe crummys and rub thy boke þerwith sore vp and downe and yt shal clense yt

Formally a recipe text, this advice relies on just a single ‘ingredient’: bread. And while bread features widely in culinary and religious texts, in the proverbial diet of prisons (bread and water) and the pairing of ‘bread and salt’, this early mention of bread in cleaning instructions deserves more consideration. It bridges the recipe genre, bread as a culinary product of the kitchens and its alienated, secondary use that relies on its texture and other material qualities. Moreover, this text draws silent parallels with contemporary instructions for the cleaning of pots and pans, tools and instruments. I wonder whether the abovementioned technology might discover trails of bread across manuscript pages?

Modern Books and Wonder Bread

An early advertisement for Wonder Bread. Found on the Blog of the Tenement Museum
An early advertisement for Wonder Bread. Found on the Blog of the Tenement Museum

Bread as a cleaning device for books continues until today, and may be familiar to some readers of this blog, especially those dealing with books or paintings in a professional or otherwise intense capacity. The American loaf known by the modest name of Wonder Bread is said to have particularly good cleansing power. Pertinently, the V&A, however, includes this practice in its category ‘What not to do…’:

Don’t use old fashioned cleaning remedies

Bread is a traditional dry cleaning material used to remove dirt from paper. If you rub a piece of fresh white bread between your fingers, you will see that it is quite effective in picking up dirt. The slight stickiness of bread is the reason why it works and also why it can be a problem. It can leave a sticky residue behind that will attract more dirt. Oily residues or small crumbs trapped in the paper fibres will support mould growth and encourage pest attack.[4]

This piece of advice forms the antidote to the abovementioned instruction for cleaning books: conflicting advice across the centuries.

Undecided on the issue I will, however, continue to make sure my hands are clean as I continue through manuscripts with recipes, especially the alchemical ones. You never know what may have left that stain in the margin.

I would like to extend my thanks to the Free Library of Philadelphia for the kind permission to use an image from their collections in this blog post.

The Tenement Museum’s blog post on the history of bread (whence the second image above originates) is not directly connected to this particular post’s themes but an interesting read for different reasons: Judy Levin, ‘From the Staff of Life to the Fluffy White Wonder: A Short History of Bread’ (19 Jan 2012).

[1] Kathryn M. Rudy, ‘Dirty Books: Quantifying Patterns of Use in Medieval Manuscripts Using a Densitometer’, Journal of Historians of Netherlendish Art 2:1-2 (2010).

[2] See this guest post by Thijs Porck at medievalfragments: ‘Paws, Pee and Mice: Cats among Medieval Manuscripts’.

[3] ‘squagen (v.) [Origin unknown; ?= squachen v.] To make a stain, smudge; also, dirty (sth.), smudge, stain.’ MED.

[4] V&A, ‘Caring for Your Books & Papers’ (accessed 25/11/2013).


Author Bio

Anke Timmermann is an antiquarian book specialist and historian of science, with a scholarly focus on the history of alchemy and medicine. She recently set up as an independent bookseller as A T Scriptorium in London, and is an Associate Member of the Antiquarian Booksellers’ Association as well as a Fellow of the Linnaean Society. Anke previously worked at one of the oldest antiquarian booksellers in London, Bernard Quaritch Ltd, following her Munby Fellowship in Bibliography at Cambridge of 2013-2014 and a career as a historian of alchemy.

When Does a Drug Trial End?

By Justin Rivest

An eighteenth-century proprietary medicine vendor. Detail from “Le Charlatan, 1785.” Hand coloured etching and aquatint. Antoine Borel after J. Augustin L’Eveillé. Source: Wellcome Images.

The question I’d like to begin this post by asking is, When does a drug enter “normal use”? Is a trial a “provisional” phase, that reaches a definitive end, say when “proof” is found, or when the relevant authorities are convinced? Or in an age where drug monopolies were insecure and difficult to enforce, was the state of trial—l’épreuve—always ongoing?

This question first crossed my mind while preparing my contribution for the recent special issue of the Bulletin of the History of Medicine, “Testing drugs and trying cures,” edited by Elaine Leong and Alisha Rankin. My article focuses on the role of patient trials in granting monopoly privileges for proprietary drugs in eighteenth-century France. These royally-granted privileges were the distant ancestors of modern drug patents. They gave their inventors a legally enforceable monopoly over the drug in question by enabling them to fine counterfeiters.

Even after they were granted monopoly privileges, drug vendors continued, almost compulsively, to gather further evidence of the effectiveness of their drugs. This evidence often took the form of an attestation or certificat. These documents could take several forms: some were notarized statements, made by a patient declaring that he or she had been cured of this or that condition. Others were endorsements signed by an expert practitioner—a famous doctor, a representative of a local college or guild—who had personally witnessed the drug’s effects.

In this post, I will use the practice of what we might call “cure attestation collection” to question whether “trials” (épreuves) of a drug really had an end from the perspective of early modern drug monopolists.

The most important reason to continue gathering documentation of the effectiveness of their drug was to convince authorities to renew their privilege at a later date, as most monopoly privileges had fixed terms of three, ten, or fifteen years. But even within these term limits, they did not have perfect guarantees. Early modern drug monopolies were tenuous. Vendors knew that they might even have to re-submit both their drugs and their documentation for arbitrary re-examination by the authorities.

Even barring arbitrary re-examinations, the multi-generational duration of many early modern monopolies meant that they would be evaluated more than once by the authorities. The drug monopoly I studied in my article, the poudre fébrifuge of the Chevalier de Guiller, was particularly long-standing, extending across four generations. As a febrifuge, the drug was targeted at “intermittent fevers,” an important cause of mortality in the French army in this period. The drug was first awarded a monopoly privilege in 1713, at the end of the reign of Louis XIV. Its inheritors faced various challenges in exploiting it over the coming decades, but they consistently managed to get the privilege renewed. By the 1770s, in fact, the latest inheritors, the sisters Marie-Thérèse and Marie-Victoire de La Jutais, had accumulated a veritable archive of attestations in favour of their drug, spanning over sixty years.

Most of these documents were cure attestations and endorsements from patients, and prominent medical practitioners. A signed personal endorsement of the drug from the supervising practitioner was often the most important result of a hospital trial. Vendors who sold drugs in bulk to the state, especially to the military, could appeal to a special type of attestation. The La Jutais sisters, for instance, did not just rely on the documents that had been handed down to them through their family. They also went to government archives—much as historians do today—looking to collect documentation that might endorse their drug. They paid the navy office to make official copies of fifty-year-old correspondence concerning their drug so that they could submit it with their petition to renew their monopoly.

Monopolists were not, however, impartial researchers. The La Jutais sisters seem not to have collected any documentation which might cast their drug in a negative light—or at least, if they came across such evidence, they avoided disseminating it. Indeed, during my research I came across several documented cases of ambiguous or negative patient trial results of the poudre fébrifuge. In one 1714 trial involving “twenty or thirty” patients at a navy hospital, the drug was deemed to be too inconsistent in its effects and was dismissed as a violent purgative rather than a true febrifuge. It seems at least plausible that the La Jutais sisters’ archival searches might have drawn up this material as well. Nonetheless this report is notably absent from their petitions for monopoly renewal in the 1770s.

The “selective archive” of positive attestations that the La Jutais sisters assembled helped them to renew their monopoly privilege in 1775. We can see from their case that early modern drug monopolists had good reasons to keep collecting cure attestations wherever they could get them. They had the effect of turning the drug’s everyday use into a form of legally acceptable evidence, making a successful trial out of every cure.


Justin is a postdoctoral researcher at the University of Cambridge and his work focuses on early drug monopolies and the role of bulk drug producers and consumers in the early modern medical marketplace. He recently co-wrote a short piece in The New England Journal of Medicine with Alisha Rankin on this topic, as well as an article in the Canadian Journal of History on one particularly successful drug entrepreneur, Adrien Helvétius (1662-1727), who sold massive quantities of his drug against dysentery to the French state for use in the army and rural poor relief efforts. His research has shown that trials on patients played a critical role in licensing early drug monopolies as well as in helping entrepreneurs secure lucrative supply contracts with the state.

Anecdotes and Antidotes

By Alisha Rankin

How did early modern individuals test and try their recipes and cures? This question is at the heart of the special issue of the Bulletin of the History of Medicine, “Testing Drugs and Trying Cures in Medieval and Early Modern Europe,” in which I participated as both a co-editor and an author. My article, “On Anecdote and Antidotes: Poison Trials in Early Modern Europe,” examines the ways in which early modern practitioners tested a specific kind of cure: antidotes to poison. It contains some information I discussed in earlier posts on this blog – here and here – but adds many details and thoughts about testing in general. Most cures, I argue, tended to be tested in the course of regular clinical experience. A patient got sick; a practitioner tried a particular remedy, observed the results, and frequently shared anecdotes of success or failure. The scale of this kind of testing could be small or large, but in most cases it involved patients who were already sick.

Poison antidotes were a little different, because practitioners could actually create the condition of illness by giving poison to a test subject. In 1563, for example, the royal surgeon to Holy Roman Emperor Ferdinand I, Claudius Richardus, wrote a letter describing the marvellous virtues of bezoar stone. As avid Harry Potter readers will know, bezoar was an animal byproduct prized as a poison antidote and cure-all. Richardus recounted a series of marvellously successful tests he had conducted on bezoar at the Emperor’s behest. In two of them, patients received bezoar in the midst of a serious illness – the usual practice. In the other two, bezoar was tested in contrived trials on condemned criminals.[1]

Bezoar stones from the imperial Kunstkammer, Kunsthistorisches Museum Vienna. Photo by Alisha Rankin.

This second kind of test – which I call a poison trial – has a long history dating back to antiquity. Many ancient kings, most famously Mithridates VI of Pontos (135-63 BCE), used condemned criminals to test poison antidotes, from which he developed his famous antidote and cure-all, mithridatium. The Greco-Roman physician Galen reportedly tested theriac, a derivative of mithridatium, on roosters, and versions of this test appeared in the writings of several Arabic physicians, including Avicenna’s highly influential Canon of Medicine.[2] Medieval physicians repeated the description of Galen’s test as well. However, poison trials tended to be described as theoretical tests that one could conduct rather than as anecdotes about tests that had actually taken place, and they were mainly suggested as a means to test whether a batch of theriac was inferior, fraudulent, or old – not whether theriac actually worked. From the time of Galen, moreover, poison trials were conducted exclusively on animals, not humans. The dominant argument for the efficacy of these drugs remained anecdotal reports of their use on sick patients.

In the Renaissance, poison trials expanded significantly, as did their role in medical communication. From the 1520s, powerful rulers began to revive the gruesome tradition of using condemned criminals to test a variety of poison antidotes – not just theriac. In addition, these tests were reported and circulated as anecdotes rather than being described as theoretical suggestions. The first known example comes from Rome in August 1524, when Pope Clement VII directed his medical personnel to test an antidote oil created by the surgeon Gregorio Caravita. He granted the medics two Corsican criminals who had been condemned to death by beheading. Both prisoners were given a strong dose of the deadly herb wolfsbane (aconitum napellus). Caravita then anointed one prisoner with the oil. The other, a “savage spirit,” was given no antidote. The first man survived; the other died in much agony.

Testimonium de verissima ac admirabili virtute olei compositi contra pestem & omnia venena (Rome, 1524), BNF.

A second successful test was conducted on a Mantuan prisoner given arsenic. Soon thereafter, the medical personnel published a public service pamphlet describing these trials in detail.[3]

A shorter version of this anecdote also appeared in the famous herbal published by Italian physician Pietro Andrea Mattioli in 1544 (with a Latin version in 1554). Mattioli’s influence helped spread poison trials around Europe. From 1561-67, a number of contrived trials on condemned criminals took place under powerful princes, including Emperor Ferdinand I, King Charles IX of France, and Duke Cosimo II de’Medici. Significantly, royal physicians and surgeons spearheaded these poison trials, and they communicated the results in anecdotes that appeared both in private documents and printed books. Claudius Richardus’s bezoar trials were part of a series of such events.

These anecdotes demonstrated careful thought in how the trials were devised and conducted. They described the trials in in excruciating detail, including the number of times a prisoner had vomited and defecated as well as the hour at which these events had occurred. In some cases, physicians attempted to created conditions that would lead to a useful outcome. Richardus’s letter described how food was withheld from a prisoner before the test, “so that one could be more certain of the trial.” This step came in response to a previous case in which the physicians had trouble getting the poison to work. Finally, physicians took care in reporting and circulating their reports about the trials, clearly imbuing them with significance. A series of poison trials on dogs conducted in 1580 by a German prince circulated in both manuscript and print as a detailed Observatio, a report intended to be shared.

Poison trials represented only a miniscule part of drug testing in early modern Europe. Indeed, anecdotes about drugs used successfully on sick people helped drive the interest in new drugs from around the globe, as described in this post by R.A. Kashanipour. Nevertheless, the anecdotes about antidotes demonstrated significant developments in both testing practices and medical communication. To find out more, read my article!


[1] Richardus’s letter, to Archbishop Nicholas Olahus, was later published in Latin and German. Thomas Jordan, Pestis phaenomena (Frankfurt, 1576), 621–630; Johann Wittich, Bericht von der wunderbaren bezoardischen Steinen (Leipzig, 1592), 21.

[2] Galen’s poison trial appeared in the treatise On Theriac to Piso, which may be spurious. However, scholars in the Islamic world and Europe assumed it was authentic. See Robert Leigh, On Theriac to Piso, Attributed to Galen: A Critical Edition with Translation and Commentary (Leiden: Brill, 2016).

[3] The pamphlet was signed by the physician Paolo Giovio, the apothecary Tomasso Bigliotti, and the senator Pietro Borghese. Testimonium de verissima ac admirabili virtute olei compositi contra pestem & omnia venena (Rome, 1524).

Tales from the Archives: Testing Drugs and Trying Cures Workshop Summary

In September 2016, The Recipes Project celebrated its fourth birthday. We now have over 500 posts in our archives and over 120 pages for readers to sift through. That’s a lot of material! (And thank you so much to our contributors for sharing such a wealth of knowledge on recipes.) But with so much material on the site, it’s easy for earlier pieces to be forgotten. So, the editors have decided that, every now and then, we’ll pull something out of the archives to share with our readers anew.

Over the next few weeks, The Recipes Project will feature a selection of case studies from the current issue of the Bulletin of the History of Medicine on “‘Testing Drugs and Trying Cures”. This special issue grew out of a 2014 workshop held at Max Planck Institute for the History of Science in Berlin. We were very lucky to have two then graduate students Ashley Buchanan and Tillman Taape, join us for and grateful that they took the time to pen the post below. It seems fitting to begin this month on testing drugs and trying cures with a revisit to their post. Elaine (editor).


By Ashley Buchanan and Tillman Taape

What did it mean to test a drug or try a cure in the early modern world? This was the central question for a group of scholars who gathered for a workshop at Max Planck Institute for the History of Science in Berlin, Germany.  Since recipes emerged as one of the key themes throughout the workshop, and because the conference’s location in Berlin made it difficult for scholars outside of Europe to attend, we thought we might share a brief summary of the “Testing Drugs and Trying Cures” papers, in the hopes that we could bring the workshop’s key ideas and discussions to a larger audience.  What emerged from an exhilarating two days of discussion and debate was the conclusion that historians of science and medicine should not privilege experiment and experimentation as fixed categories, but should understand the multiple ways in which physicians, apothecaries, artisans, institutions, and individuals in the early modern world tested, tried, investigated, experienced, modified, observed, and measured medicinal remedies and materiae medicae.

As written forms of medical and pharmaceutical knowledge and practice, recipes played an important part in the testing of drugs and cures, and our discussion raised larger questions surrounding the nature and purpose of an early modern recipe.

A miniature depicting the Schola Medica Salernitana from a copy of Avicenna’s Canons.  From Wikimedia Commons.

Michael McVaugh’s paper opened the discussion by exploring how medieval physicians went about testing drugs. Learned doctors in the Middle Ages might appear helplessly hidebound, and inclined to follow ancient authorities over experimentation. In contrast, McVaugh showed how a group of Montpellier physicians in the fourteenth century established something of an experimental program. Medieval physicians, however, were not testing to find a cure, but to determine the quality, strength, and effectiveness of a drug as it pertained to a particular person’s complexion. McVaugh underscored an important difference in the purpose of medieval drug testing. Physicians tested not for universal effectiveness, but to determine the quality of a drug – was it hot, cold, moist, or dry.

Title page of the Academy’s Observations sur les eaux minérales (1675). From

Although it became clear in our roundtable discussion that we should be wary of labeling such practices as obvious precursors to the experimental philosophies of the Scientific Revolution, many of the papers showed that the importance of specific tests resonated throughout the early modern period. Evan Ragland’s paper, for example, traced the use of the phrase periculum facere (‘to make a trial’) in physicians’ writings on medicine, anatomy and chemistry. Similarly, Michael Bycroft showed that French physicians and chemical experts of the Académie des Sciences became increasingly interested in the exact composition of mineral waters. Contrived tests such as color indicators or the analysis of residues after evaporation increasingly became the touchstone of proper inquiry.

McVaugh, Ragland, and Bycroft’s papers all underscored the need to understand the specific nature and purpose of testing in each historical context. Continuing to emphasize the importance of historical context, Francesco Paulo de Ceglia’s paper showed just how different the purpose of testing could be in the context of seventeenth century blood miracles in the Kingdom of Naples. Catholics tested the liquefaction of the blood of their patron saint to explore the limits of nature. By discovering nature’s limits, you could then determine what was truly miraculous. Protestants, on the other hand, tested various materials and recipes to recreate the liquefaction of blood to cast doubt on the alleged miracle.

Reliquary containing a glass ampoule of San Gennaro’s blood. From La Repubblica.

In the context of testing, drugs and cures are often under scrutiny in the form of recipes detailing their production and administration. While recipes emerged from many of the papers as very important forms of knowledge, it proved virtually impossible to define exactly what a recipe was. Recipes can be very short or very detailed, ranging from a mere list of ingredients to careful step-by-step instructions. If there is one thing recipes have in common, it is the need for testing, trying, modifying and adapting to different conditions. While constructing an all-encompassing definition of a recipe proved futile, all agreed that it was fruitful to understand recipes as an important genre in early modern science and medicine.


For her investigation on the testing practices of Venetian apothecaries, Valentina Pugliano emphasized the difference between experiment and experience. Venetian apothecaries were less concerned with testing drugs (in a traditional sense) than they were with the experience or truthfulness of their ingredients. Testing by inspection, smell and taste was also important in this pharmaceutical context, to ensure that the ingredients were what the merchant had promised them to be, and not a cheap substitute with inferior properties. For Pugliano’s apothecaries, the important issue that required testing was the authenticity of the ingredients rather than the efficacy of the finished product; after all, most preparations had proved their worth since antiquity. Like McVaugh, Pugliano questioned traditional “Baconian” understandings of what it meant to experiment and test and argued for more nuanced notions of testing and trying, which included observing, measuring, evaluating, and experiencing.

Title page of Johannes Christophorus Homann’s Dissertatio inauguralis medica de medicinae cum geosophia nexu quam auspice deo prpitio (Hala Madgeburica, Hendelius, 1725). From

With early modern Europeans’ increasing forays into the New World, however, more and more materiae medicae were found which were absent from ancient medical writings. Pliny and Dioscorides were silent on such substances as guaiacum wood, Peruvian bark or New World balsam, so their medicinal properties had to be newly investigated. Antonio Barrera-Osorio and Samir Boumediene’s papers added America, or the New World, into the discussion. Both emphasized the role of new drugs and materia medica in the rise of European experimental practices. New drugs and new medicinal recipes required new ways of testing.

Antonio Barrera-Osorio’s paper argued for an empirical culture in the Spanish empire, which was well suited to respond to these challenges. He showed how his protagonists gathered information about New World remedies from natives or travellers and experimented with ways of preparing them. Some of these drugs and recipes were deemed so important for the economy and health of the empire that the Spanish crown ordered tests in hospitals all over Castile. Samir Boumediene’s paper elaborated on the issue of making workable recipes for newly discovered drugs. Once more, taste and smell were important assays, but drugs such as guaiacum and Peruvian bark were also tested on a larger scale. Dispensing them to the poor inmates of charitable hospitals (as happened in France and Germany) helped to determine their effect, and to establish recipes, which indicated how to adjust the treatment in individual cases.

Andreas Cleyer, Specimen Medicinae Sinicae (Frankfurt, 1682). From

Gianna Pomata and Marta Hanson’s paper showed how recipes also functioned as vehicles of knowledge between different cultures. Recipes, as either formula or prescription, were both found in European and Chinese medical cultures. According to Pomata and Hanson, it was the familiar genre of the recipe that facilitated the transmission of Chinese pharmacology to Europe in the second half of the seventeenth century. Similarly, Carla Nappi argued that the Manchu medicinal recipes of the Qing court were spaces of encounter and medical translation in the early modern world. Pomata, Hanson, and Nappi demonstrated how the recipe served as the common ground between European and Chinese medicine and made the translation of Chinese pulse medicine and the transmission of Chinese materia medica possible in the seventeenth and eighteenth centuries.

Although recipes are difficult to characterize as a genre, it is clear that they are fascinating objects of historical study. More often than not, they are fluid rather than fixed forms of knowledge, requiring adaptation at every turn. They bring together ingredients, practices and often practitioners from all over the world, and themselves have a tendency to aggregate into larger collections. As written manifestations of gestures and processes, they play an important part in testing, assessing and modifying drugs and cures.