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Many, Many Experiments

Many, Many Experiments

(p.28) Chapter Two Many, Many Experiments
About Method
Jutta Schickore
University of Chicago Press

Abstract and Keywords

In the mid-seventeenth century, experiments on snake venom were conducted within the larger contexts of discussions about body functions and the nature of disease; about blood, its role in the body, and its circulation; about nerve function and the theory of animal spirits; about chemical and mechanical philosophy; about iatrochemistry; and about the analogy between the actions of poisons and the actions of specific medicines. Francesco Redi’s extended studies of viper venom showed that a substance was responsible for the adverse effects of the bite—namely, the “yellow liquor” that was discharged from the viper’s teeth. Taken by mouth, this substance was innocent. Put in wounds, it was fatal to humans and animals. Moyse Charas, his French adversary, turned against Redi and argued that the rage of the viper was responsible for the fatal effects. These writings on venom exemplify how more concrete methodological views and conceptions of experimentation were integrated in experimental reports to establish proper procedure. Two experimental strategies stand out: comparisons and repetitions. The chapter argues that repetitions, not comparisons, were the new feature in Redi’s experimental project.

Keywords:   snake venom, methods discourse, experimentalism, experimental reports, repetition, Francesco Redi, Moyse Charas

Historians of Italian science have argued that the work carried out at the Accademia del Cimento was primarily a manifestation of courtly life, shaped by the directives of the Medici.1 The Proem of the Saggi di naturali esperienze in fact expresses various general commitments of the members of the Cimento Academy: commitments to their patrons, commitments to experience, and commitments to the authorities of the “new science.” The reports of experiments that were carried out in the context of the academy reflect these larger commitments, but the methods discourse is often significantly more elaborate than the general views expounded in the Proem of the Saggi di naturali esperienze. Francesco Redi’s extended studies of viper venom illustrate how more concrete methodological views and conceptions of experimentation were integrated in experimental reports to establish proper procedure.2

Snakes were in many respects significant to savants in early modern Tuscany.3 The scholars were well versed in a long and rich tradition of snake symbolism, and they were specifically interested in the role that snakes played in therapeutics. The meat of vipers was an essential ingredient of theriac, an ancient remedy for snakebite and various other health troubles.4 Many investigations of snakes and snake venom were undertaken for the straightforward practical reasons of finding an antidote for calamities produced by snake bites and of exploiting the assumed medicinal function of viper meat. Experiments on snake venom were conducted within the larger contexts of discussions about body functions and the nature of disease; about blood, its role in the body, and its circulation; about nerve function and the theory of animal spirits; about chemical and mechanical philosophy; about iatrochemistry; and about the analogy between the actions of poisons and the actions of specific medicines. All (p.29) these issues are reflected in the debates about the nature and working of the venom, possible treatments, and antidotes.

Refuting Old Fables through Many Experiments

Redi’s extended study of viper venom began in the early 1660s. He mostly relied on animal experiments, but he also used some evidence from dissections of snakebite victims as well as from observations of the effects of snake venom on humans. Redi presented the report of his observations and experiments, the Observations on Vipers (1664), in a letter to the secretary of the Cimento Academy, Count Lorenzo Magalotti. The substantial letter comprises discussions about the nature and status of experimental evidence; a survey of a range of sources pertaining to snake bites and snake venom, beginning in antiquity; and a novel interpretation of the nature of snake venom together with reports of supporting experiments that Redi and his colleagues had performed. A second letter was published in 1670 as a response to criticism leveled by the renowned French apothecary Moyse Charas (although, as we will see later, it was not addressed to Charas).5 The second letter, as well as the dispute about the nature and operation of viper venom that unfolded between Redi and Charas, will be considered in the next chapter.

Redi commenced his work at the request of the Grand Duke of Tuscany, Ferdinando II, who urged Redi to investigate the nature of the venom, including where it was stored and how it worked. For his experiments, Redi could make use of the numerous vipers that had been sent to the court from Naples for the production of theriac. The letter contained Redi’s answer to the request. A substance existed that was responsible for the adverse effects of the bite—namely, the “yellow liquor” that was discharged from the viper’s teeth. Taken by mouth, this substance was innocent. Put in wounds, it was fatal to humans and animals. The letter also provided an opportunity for Redi to outline some concrete ideas about how to perform experiments successfully.

Redi’s letters have been read as a direct response to aristocratic interests and expectations at the Tuscan court.6 Historians of early modern Italian science have suggested that the expectations of the members of the Tuscan court shaped the narratives of the experimenters’ projects. The narratives had to present subjects worthy of the status of the patrons and had to make the study of nature “lavish, costly and entertaining.”7 Redi’s account of the experiments with vipers was certainly engaging (p.30) and thrilling, full of curious and gory details. Nothing could be farther from the dry, standardized, and schematic protocols we find in modern scientific journals. For instance, to establish whether the bile of the viper was a poison, as traditional sources had it, Redi deferred to the testimony of Jacopo Sozzi, the viper catcher. He gave a vivid description of Jacopo’s performance. The man listened to the learned dispute about the effect of viper bile and was “just able to contain himself so as not to laugh” and then, “grinning, he took a viper’s bile and diluting it with half a glass of fresh water, tossed it off with unflinching face; he gave to understand how mistaken the above-mentioned authors were.”8 Jacopo also drank half a glass of wine mixed with “all the liquor” and “all the foam and saliva that this excited, irritated, pressured, beaten serpent could shoot forth”; he drank this concoction “as if it had been so much pearly julep.”9

Such stories are more than vignettes for the amusement and thrill of patrons, however. Redi’s letter draws on these episodes to advocate experimentalism and to stake a claim, and the descriptions of the trials in his letter also indicate that the experiments were performed reliably. Paying attention to the different layers of methods discourse helps show how Redi’s letter does all these things to good effect.

The authors of the Saggi di naturali esperienze attempted to strike a balance between commitments to the “new” experimental method and commitments to various authorities, patrons, and traditions old and new. Redi’s letter employed the same technique. It begins with ideas and formulations taken from the Saggi. Like the Saggi, the letter is framed with a plea for experience as the ultimate arbiter of truth. It opens with Redi’s affirmation that he found himself ever more “firm in my attention of not trusting the phenomena of nature if I do not see them with my own eyes.” Like the authors of the Saggi, Redi stressed that experimental evidence outweighed the word of authorities, and he was also quite explicit about the need to check ancient authorities’ views against experience. He assured his readers that he “loved” the ancient philosophers—Thales, Anaxagoras, Plato, Aristotle, Democritus, Epicurus, and all the other “princes of philosophy”—but insisted that not all they had written was true. Time and again Redi emphasized the importance of experiment, criticizing those who blindly followed the ancients, those who “put their hands over their eyes,” and the inveterate fool who refused to look through Galileo’s telescope so that he could continue to repudiate Galileo’s findings.10

As a leading member of the Accademia della Crusca, Redi was at the same time appreciative of the Tuscan literary and cultural heritage. In his letter to Magalotti, he paraphrased Dante,11 and he did so to claim that one (p.31) should not follow authorities blindly. He noted that many writers, ancient and modern, were “like parrots, they write and read and they believe the most solemn untruths coming from the most credulous and inexperienced of common scribblers, those with the finest quality of sickening brilliance.”12

In the mid-seventeenth century, numerous wondrous tales surrounding snakes and snake bites existed, such as the notion that if a serpent was put in the middle of a ring made from the foliage of betony, it would beat itself to death with its tail—or the notion that it was fatal to drink the wine from a bottle in which a viper had drowned. Previous and contemporaneous authorities had suggested that it was the viper’s bile that caused harm, that certain body parts (such as the head) were poisonous, or that the harmful effects of the bite were caused by something immaterial.

Redi reviewed some of the older tales and beliefs about snakes, such as, for instance, in his discussion of the likely causes of Cleopatra’s death, Jay Tribby’s prime example of Redi’s conversation with ancient authorities.13 Redi, insisting that ancient beliefs must be critiqued in light of new evidence, offered accounts of his own experiments in response to the ancient fables. According to Tribby, the episode with the viper catcher who swallows bile in a public demonstration is exemplary for the confrontation between a “tradition of Great Texts by Great Authors”—the received opinions informing a group of onlookers—and the “bold, textually unmediated gesture” of the experimenter.14

It is correct that the spectators immediately questioned these findings, but we must look carefully at what exactly was at stake. The onlookers were skeptical because they questioned the experimental procedure. They likely did refer to a “great text” by a “great author,” but that text includes accounts of experimental trials: Galen’s treatise On Theriac to Piso. This work contains the description of a drug test strikingly similar to the experimental arrangement that Redi’s letter presents. In the relevant passage of Galen’s treatise, two trials are described. First, “poisonous beasts” are placed among wild cocks that had received theriac, and “those who have not drunk theriac die immediately, but those who have drunk it are strong and stay alive after being bitten.” In the second trial, a purgative drug is given to someone who had been given theriac. The person is not purged, so evidently the theriac could protect effectively.15

Redi reported in his letter that his critics suspected trickery: The viper catcher might have taken theriac or some other potion that acted as an antidote. Even though the viper catcher denied the suspicion, the others requested that his testimony be backed up with another test. And it is this issue that the letter then addresses.

(p.32) Redi told readers how he had established the reliability of procedure. Because the witnesses who were present were not entirely convinced by the demonstration that viper bile was harmless, the group performed animal experiments, feeding the bile to two large pigeons, a dog, and two cocks. Again, the letter offers a vivid description: A peacock and a turkey were fed two gallbladders, “and I had a cat eat four entrails without the gallbladder being removed; I can tell you that it greedily licked its lips.”16 All animals survived the meal without any ill effects.

There is more to these vignettes than just a thrilling story and a bold gesture. They also point toward concerns about whether experimental procedures are reliable and informative. These concerns are more concrete than the general commitment to experimentalism that we find in the Saggi and more concrete than the opening and closing statements in Redi’s letter, which demand that experimenters see for themselves. In Redi’s letters, the notion of repeating one’s own experiments is quite conspicuous. Early on, Redi stated that he could not trust the phenomena “if they are not confirmed by iterated and reiterated experience.”17

It has been noted that this declaration corresponds to the motto of the Cimento Academy, provando e riprovando.18 This motto is ambiguous, however, because it does not specify what it is that needs to be checked and checked again—the beliefs of the authorities? One’s peers’ experiments? One’s own experiments? Redi’s letter stressed the repetitions of Redi’s own trials.19 He noted that many experiments had been done, often multiple times. The old fables were refuted “by experiments made many many times.”20 Redi had “observed […] very often” that the yellow liquor spurted into the wound when the viper struck and killed.21 The effects of bile and of the yellow fluid were tested on a number of different animals. And Redi had demonstrated the fatal effects of venom taken from dead vipers and put in wounds in more than a hundred experiments.

Redi put much emphasis on the issue of multiple experimental trials, but it is not entirely obvious how these statements should be read. Some historians have argued that we need to take them with a grain of salt, for they, too, are reflections of the social context in which the experiments were performed. Paula Findlen, for example, has suggested reading the references to many repetitions as a political gambit to display the power of the Tuscan court. She has argued that the emphasis on many repetitions in the academicians’ writings underlined the wealth of resources the academy (and, by implication, the Tuscan court) had at its disposal.22

There is a famous passage from Experiments on the Generation of Insects in which Redi stated that he had opened 20,000 oak galls to check whether (p.33) they had spiders and had found none. In this passage, Redi turned against an opponent, Pietro Andrea Mattiuoli, who had claimed that oak galls produced spiders.23 The reference to 20,000 experiments—experiences—could plausibly be interpreted as a strategic move to impress and discourage his opponent. For Findlen, this abundance of objects was linked to truth and accuracy—Redi was obliged to settle the issues that the Grand Duke set before him “not by the powers of his own wit but by mustering the material and eloquential resources to his advantage.”24

Another possible reading of references to multiple trials would be that Redi simply borrowed the formula from an acknowledged authority on experimentation. We already saw that Galileo used the reference to “a hundred repetitions” to assure readers of the uniformity, and hence the reliability, of his experiments with falling bodies.25 Redi frequently used literary models: he rephrased in his letter some passages from the Saggi di naturali esperienze, and he also paraphrased Dante. He might perhaps have echoed Galileo’s statement in other passages, thus investing his account with authority borrowed from the eminent scholar.

The most plausible interpretation of references to multiple trials is, however, that Redi invoked repetitions for different purposes in different contexts. There is the reference to 20,000 supporting observations, which would surely impress most scholars and discourage them from opposing Redi. There are references to “many many” experiments when Redi rejected the ancients and their fables about snakes. A more oblique case is the reference to “more than one hundred experiments in various animals” when Redi reported that the venom taken from dead vipers was fatal, too, even that taken from vipers “dead for two or three days.”26 As in the experiments with oak galls, the experiments with venom from dead vipers were, in fact, a refutation of the position held by a number of Redi’s precursors and contemporaries (including van Helmont and Boyle)—that the mental or emotional state of the snake had something to do with the fatal effects. Dead snakes will not be angry.

Moreover, it is likely that Redi saw practical value in repetitions of experimental trials. At least sometimes, we should assume that the references to multiple trials described a genuine methodological strategy that he had actually followed. The literal interpretation of these references suggests itself if we consider that Redi offered explicit justifications for his methodological strategy of multiple trials.

The key experiments—the experiments with bile and the introduction of the yellow liquor in wounds—were performed on different kinds of animals and were repeated several times. In this context, Redi advanced (p.34) two justifications for repetitions of trials. He reminded his reader that “as you know well, there are many things which behave as food for some kinds of animals, that in another species produce the effects of a venom, or other unusual or annoying mishaps.”27 What was poison for one might be food for another.28 Performing experiments on different kinds of animals helped reveal these differences.

More important were repetitions of experiments on animals of the same kind. Redi expressed his astonishment about Marco Aurelio Severino,29 “most versed in knowledge of the viper and greatly experienced,” who had been convinced by “only two experiments” that the yellow liquor was not lethal when it was put into wounds.30 He insisted that “often times it happens that these genuine causes, for some unknown or unseen hindrance, cannot produce their effects.”31 Because of this possibility, it was crucial to repeat experiments many times so as to erase the effects of any unseen hindrance. We are reminded of Boyle’s concern with the “wantonness” of nature. Redi bolstered this statement with another quote from Dante, but he also described several instances in which he had experienced how his own efforts were thwarted by impediments—some known, some unknown. He had been present when “sheep, dogs, and cocks having been furiously bitten by vipers in the country at the height of the afternoon did not die”;32 he had seen a cockerel die after having been bitten by a viper whose teeth had been cut off and whose venom had been squirted out; and of the ducks and pigeons whose wounds had been smeared with venom, one had survived. Only by performing experiments repeatedly could one establish which findings were reliable.

The letter draws together narratives of experiments and methods discourse to produce an effective and forceful argument. Redi turned against traditional beliefs about snake venom and against older authorities, advancing an alternative. The letter tells us how he and his fellow experimenters had performed the trials; references to witnesses and repetitions showed that they had followed proper procedure, all while reinforcing the ideal of good experimental practice. Several experiments are described, testing the effects of bile and of the yellow liquor, and together these descriptions gently lead the reader away from the ancient beliefs about snakes: First the reader learns that viper bile was not poisonous. All experiments performed at the Cimento Academy suggested that bile was harmless when swallowed. Experiments in which bile was introduced into wounds of chicks, pigeons, a rabbit, a lamb, and a hare showed that the bile did not do any harm even when it came into contact with the blood of the victim. Then the reader (p.35) learns what happens if the yellow fluid from the viper’s teeth is taken by mouth: again, nothing. Finally, the reader learns that the yellow fluid has fatal effects when it comes into contact with blood. As a whole, the chain of experiments thus demonstrated that ancient beliefs about vipers and poisons were erroneous.

Getting the experiments and observations right, however, does not necessarily mean to be in a position to explain the findings. To those who were familiar with earlier debates, it must have been obvious that Redi’s narrative did contain an oblique reference to and an implicit refutation of the Helmontian theory of disease, but Redi did not expressly turn against van Helmont. Even after many experiments, Redi did not provide what Boyle would have called a “discourse upon experiment”: he did not attempt to explain how viper venom caused death. This was in keeping with the commitment to abstinence from theory that is expressed in the preface of the Saggi di naturali esperienze. Redi offered diverse possible explanations of the working of venom without committing himself to one. Venom might work by some unknown occult power, by cooling and freezing or heating and drying the heart, by dispersing and destroying its spirits, by depriving it of feeling—or perhaps by impeding the movement of the heart itself, making the blood congeal, or by making the blood coagulate in the veins.33 Redi declared that he found himself unable to establish which of these explanations was the correct one (if any); and he did not suggest any further experiments that might help decide between the various possibilities.

Parisian Challenge

Five years after Redi communicated the results of his research to Magalotti, he was challenged by a Frenchman. In 1669, Moyse Charas published a book entitled Nouvelles expériences sur la vipère (in English translation New Experiments [!] Upon Vipers, 1670),34 in which he cast doubt on Redi’s investigations and offered an explanation of the working of viper venom.35 Charas did not have any qualms with Redi’s claim that vipers possessed glands that produced yellow liquor—in fact he reported having observed them himself and having shown them to “knowing Physitians”—but he believed that the yellow liquor was harmless.36 He thought that the viper’s anger made its bite fatal and that theriac was an effective antidote.37

In 1670, Charas had already performed a public preparation of theriac (p.36) and had published a treatise on the panacea, which detailed the process of the preparation. The title page of his 1669 book identifies him as apothecary to the king’s brother. In 1672, he earned a leading position as sous-démonstrateur de chimie at the Jardin du Roi (Jardin Royal des Plantes) in Paris.38

Charas’s book begins with a description of the anatomy of vipers and of dissections of healthy snakes. It ends with a survey of remedies made with ingredients taken from vipers that were useful to therapeutics. In this part, no tests or experiments are described but only the preparations of the medicines, the manner in which they should be taken, and the effects they would have. For the exchanges between Charas and Redi, the middle part of the book is the most significant. It is entitled “Experiments Upon Vipérs” and comprises about 100 pages. The text describes experiments with animals—vipers biting dogs and small birds. Charas described in much greater detail than Redi had the alterations of the inner parts that could be found in dissections of the animals. Based on these experiments, Charas advanced an explanation of the nature of viper venom and explained why theriac worked against snakebite. Like Redi, Charas conducted experiments in the presence—and with the aid—of other scientific gentlemen.

Redi’s letter primarily targeted the beliefs of the ancients; indeed, even though he ostentatiously abstained from interpretations, the letter was organized in such a way that the reader could not but dismiss the tales and errors of bygone times. Charas’s book targeted Redi—or, rather, a “famous man,” a “person very intelligent” whose views were “contrary” to his own.39 It is much more explicitly an argument for (and against) certain positions, and although it does contain many descriptions of experiments, the accounts of the activities are far less entertaining and amusing. There are no grinning viper catchers, no potions, no vipers drowning in wine bottles—just reports of bites, tormented animals, dissections, and lesions.

Like Redi and many other early modern experimenters, Charas committed himself to experimentalism and distanced himself from the scholarly tradition of reasoning from first principles. His commitment to experimentation is much less explicit than the programmatic statements of the Italian academicians, being mostly conveyed through the structure of his book and the way in which the middle part of his book is organized. The book brings to mind Boyle’s strict distinction between “narratives” and “discourses upon experiments”: Charas described a number of experiments that had been done at his house over a period of a couple years—mostly experiments with dogs and small birds that were bitten in various body parts by vipers. In particular, he described, with more attention to detail and in less (p.37) colorful terms than Redi, how and where the animals were bitten and the lesions that could be found in dissections of these animals.

The dissections of dogs, pigeons, and pullets that Charas and his colleagues performed showed various degrees of alterations of the blood and coagulations in various places—for instance, around the heart and in the gut. According to Charas, the experiments and dissections clearly showed that the venom affected the blood, causing it to coagulate. He then offered interpretations of his findings, stressing that the experiments he had related inadvertently forced certain conclusions upon him—or, as he put it, “do insensibly oblige us to deliver our thoughts concerning the Venom of Vipers.”40 More experiments were then described to support these thoughts concerning viper venom, and the part ended with some general reflections on the mechanical operation of antidotes.

With respect to the methodological issues that Charas discussed, the contrast with Redi’s letter is also quite striking. We have seen that Redi highlighted one methodological strategy—the frequent repetition of one’s own experiments—and that he explicitly justified this strategy by reminding his readers of the variations among animal species and of “unseen hindrance,” the accidents and contingencies that might impede the performance of experiments. Charas obviously had Redi in mind when he performed his experiments, but he did not claim to have reproduced Redi’s, or indeed anyone else’s, experiments. Instead, he advanced his own views about the matter, supported by a description of the evidence he himself had obtained. Like Redi, he emphasized that he had performed many experiments, but he did not address the issue of impediments. Rather, he emphasized the uniformity of experimental outcomes across a number of trials. Precisely because his findings had disagreed with Redi’s, he had been particularly careful and exact, and he had confirmed his views “by a very great number of Experiments, which have always been found alike, in the truth, we here assert, and of which we shall make evident and irrefragable proof.”41

Moreover, although he did point out that he had performed a “very great” number of experiments, what he evidently meant was that he and his group had carried out numerous different experiments (as detailed in the book: each trial has its own subsection, complete with subtitle: “The Biting of a Dog in his Ear,” “Another Biting upon a Dog,” and so forth). He stated that he had performed “divers” or “many” experiments, and when on occasion he specified the number of repetitions he had performed, the numbers were comparatively small (three times, six times, certainly not “one-hundred times”).

(p.38) Unlike Redi, Charas did not shy from speculating about the mechanisms of the working of venom. These speculations informed the narrative throughout. Even his initial descriptions of bitings and dissections are permeated by references to “irritated” and “angered” snakes and “weakened spirits.” He noted, for instance, that the corruption of the blood disturbed its circulation, which “hinders the communication of the Spirits through the whole body, depriving the noble parts of them, as well as of the pure bloud, which was wont to bedew them, and destroying them indirectly, by causing this privation of Spirits and of the good liquor, whence depends their subsistence.”42 Having described these experiments and dissections, he reasoned that the ultimate cause of the fatal effects of the viper bite lay in the imagination of the viper. As he put it: “The imagination of the Viper being irritated by the idea of revenge which she had fram’d to herself, gives a certain motion to the spirits.” Charas assumed that the spirits were being pushed out through the teeth of the viper. They communicated the anger to the victim.43

Only in his second work on viper venom did Charas explicitly refer to van Helmont, but in his earlier work he evidently had the Helmontian notion of disease in mind when he treated the animal spirits as moved by some kind of vital principle that was, in turn, aroused by an irritant. The Helmontian conception had great explanatory power: It explained the difference between the bite of an angered viper and that of a viper whose jaws were forced open. The application of force made the viper retain its spirits; the freedom of action was required for releasing the spirits.44 Moreover, Charas was able to explain why the bite of a viper was less dangerous after the snake had been made to bite on a slice of bread. This was because the bread crumbs that stuck in its teeth hampered the movement of the spirits. In addition, this conception of the nature and working of the venom could also explain the power of certain remedies—in particular, volatile salt. The salt parts acted mechanically: they hooked themselves onto the vexed spirits and drove them out of the body.45

The experiments that are described after the thoughts he had felt obliged to deliver to the reader all supported this explanation. The experiments not only confirmed that the yellow fluid was harmless when ingested but also showed that the yellow liquor was harmless when introduced in a wound and that the bite of an angered snake was fatal even when no yellow liquor was involved. What is notable about these experiments is that Charas derived the main support for the position from comparisons. These comparative trials were designed specifically to establish the causes (p.39) of observed effects—a task that must come after the careful observation of effects, as Charas pointed out. Echoing Bacon, he said that the plan for his book was to describe the search for causes only after various experimental effects had been described, he was not entirely consistent in the execution of his plan. The experimental part begins with descriptions of dissections of various birds after they had been bitten—they all showed the same lesions. But in one section, entitled “EXPERIMENTS of the Biting of Vipers, made upon Pigeons and Pullets,” Charas reported a more informative trial, as if he wanted to give the impatient reader a glimpse of what was coming later. That trial involved a comparison and conclusions drawn from it and should thus have been discussed in the last interpretive section of this part: “it will not be amiss,” he wrote (although, by his own standards, it was!) “here to relate the different success in two Pigeons, we caused to be bitten equally and in the same place by an angered Viper. One of them we made to swallow the weight of about half a crown of Theriack, a moment before it was bitten, giving nothing to the other.”46 The former survived, the latter died in half an hour. The surviving bird was bitten again after the first ordeal and died from the second bite.

The point of this comparison was, of course, to demonstrate that the “different success” of the two trials was due to the presence and absence of the presumed cause for the recovery: theriac. Charas added an interpretation to his finding—strictly speaking, also out of place in this particular part of the book—in which he explained the different success as a result of the battle between the joint forces of animal spirits and theriac and the evil spirits of the viper.47

That same comparative strategy is used to great effect in the second, “demonstrative” section of the experimental part of the book. Charas devoted an entire chapter to the question of whether the yellow liquor was fatal, marshaling evidence from comparative experiments designed to answer that question. Some experiments examined the effect of the yellow liquor alone and found it ineffective; others examined the effect of the bite of angered vipers without yellow liquor involved and found it lethal.

A pigeon wounded under the wing and in the leg received some yellow liquor “drawn from the gums of two enraged Vipers,” and both wounds were immediately covered to prevent the venom from flowing out.48 The pigeon was not affected, and the wounds healed. A cat, several pullets, and more pigeons were treated in the same way, “alwayes with the like success, and without any offence to the Animals.”49 The same trial had been repeated on a dog—three times, even twice in one day. Charas (p.40) stressed that the dog had been wounded toward the bottom of the ear so that it could not lick the wound, and “no mischief at all” had followed.

Charas described experiments specifically designed to show the effect of the snake’s anger. He referred to comparisons of “the biting of the Viper angered” and those of “a Viper, which was made to bite by holding its jaws, and by passing its great teeth into the body of some animal” (a procedure that we may assume would not anger the snake). He found “a quite manifest difference” between the effects of the bite of an angry viper and that of a viper that was not angered. In the second case, the wound healed and no “sinister accident” occurred.50

A pigeon died from a bite even though the viper had first been made to bite several times on a slice of bread (so that no yellow liquor could have been left in the teeth). The pigeon died slowly, but that, Charas explained, was because the bread crumbs had stopped the pores of the teeth and thus impeded the exit of the vexed spirits. The main point was that the death had occurred “without any mixture of the juyce which had been altogether emptied.”51 In all these experiments, comparisons of trials are described to demonstrate that certain factors are responsible for certain observed effects.

Redi emphasized multiple trials; in Charas’s work, the emphasis is on comparisons. It would be mistaken to assume that comparative trials were more advanced or sophisticated experimental strategies than “mere” repetitions, however—repetitions of trials and comparative trials have different purposes. Repetitions have practical relevance and are employed to deal with practical challenges. They are performed to stabilize an experimental situation and to make the findings more secure. A comparative trial, by contrast, is the precondition for a process of reasoning from experiment.

Charas’s reasoning immediately reminds us of Bacon’s new scientific method and his conception of privileged instances, specifically the fourteenth of those: the “decisive instance” or instance of the crossroads. But we need to consider this carefully. For Bacon, the instances of the crossroads are crucial instances in that they show which of two possible causes (or forms) is the true cause of the nature that is being investigated. Bacon characterized these decisive instances as very illuminating, being invested with great authority.52 Notably, however, Bacon’s point was about the function of these instances. Certain observations or experiments were called “crucial” not because they had a specific identifiable structure but rather because they could demonstrate a certain contested position or help decide between two alternative hypotheses. The various experiments that (p.41) Bacon discussed to illustrate the fourteenth of his privileged instances for inductive reasoning fill this role, as does Newton’s famous experimentum crucis from the Opticks.

On the other hand, a number of examples of comparative experimental trials precede Charas’s work as well as Bacon’s; indeed, I have already drawn attention to Galen’s experiments with cocks and theriac. Another example, and one that might well have been known to Charas, is Bernard Gordon’s investigation of theriac as an antidote to poison, which includes a comparison of this type.53 Gordon, too, examined the efficacy of theriac, proceeding just as Galen had. He advised that the experimenter “take two pheasants, cut off their crests, apply a poison to the wounds (or administer it orally) and wait until they begin to stagger. Then put theriac on the crest wound and in the drink of one of them: if this one lives and the other dies, the theriac is good.”54 Considering that there were prominent precedents of comparative experimentation, it is not surprising that neither Redi nor Charas commented much on the practice itself. For them, performing many experiments—numerous, and repeatedly—was the strategy worthy of note.

Reading Charas’s treatise with Redi’s letter in mind helps us see that an overall commitment to experimentalism can be realized in quite different ways. Both Redi and Charas were experimentalists, both called for many experiments, and both demanded that interpretations and thoughts be based strictly on their outcomes—but they had different understandings of what it meant to carry out many experiments. The two investigators highlighted different strategies for establishing proper procedure. Only Redi expressed concern about the “wantonness” of nature; presumably this had something to do with his repeating his own experiments much more than Charas repeated his. In the second round of their dispute, the discrepancies between the two approaches would become more apparent. The dispute was also an occasion for more explicit reflections on exactly how the experimentalist imperative should be put into practice as well as on how the practical challenges of experimenting with living beings could be addressed.


(1.) For secondary sources on the Accademia del Cimento, see, among others, Mario Biagioli, “Etiquette, Interdependence, and Sociability in (p.239) Seventeenth-Century Science,” Critical Inquiry 22 (1996): 193–238;; Marco Beretta, “At the Source of Western Science: The Organization of Experimentalism at the Accademia Del Cimento (1657–1667),” Notes and Records of the Royal Society of London 54 (2000): 131–51; and Boschiero, Experiment and Natural Philosophy in Seventeenth-Century Tuscany.

(2.) Luciano Boschiero, “Natural Philosophizing inside the Late Seventeenth-Century Tuscan Court,” British Journal for the History of Science 35 (2002): 388.

(4.) On theriac, see G. Watson, Theriac and Mithridatium: A Study of Therapeutics (London: Wellcome Historical Medical Library, 1966); and, more recently, Christiane Nockels Fabbri, “Treating Medieval Plague: The Wonderful Virtues of Theriac,” Early Science and Medicine 12 (2007): 247–83.

(5.) Redi was also involved in a controversy with the Jesuit Athanasius Kircher on the efficacy of snake stones as a remedy for snakebite; see Baldwin, “The Snakestone Experiments.”

(8.) Peter K. Knoefel, Francesco Redi on Vipers (Leiden: Brill, 1988), 6.

(9.) Ibid., 7.

(10.) Ibid., 3, 23.

(11.) Francesco Redi, Experiments on the Generation of Insects (Chicago: Open Court, 1909), 20.

(15.) Leigh, “On Theriac to Piso,” 59. In Galen’s text, the purpose of the second trial was to test the quality of the antidote—if the person who took it and was (p.240) not purged by the purgative, the theriac must be of high quality. The design of the trial was very similar to the one that Redi described. Redi did not refer to Galen in the context of this passage, but he mentioned Galen in other parts of his letter (along with Avicenna’s work on drugs), so he clearly considered Galen’s work as an important context for the experiments he described.

(16.) Knoefel, Francesco Redi on Vipers, 6. “Another test” is Knoefel’s translation of altre prove. I quote the Italian text following the second edition of Redi’s Opere; see Francesco Redi, “Osservazioni Intorno Alle Vipere,” in Opere di Francesco Redi (Naples: A spese di R. Gessari, nella stamperia di A. Carfora, 1740–1741); and Francesco Redi, “Lettera Sopra Alcune Opposizioni Fatte Alle Sue Osservazioni Intorno Alle Vipere,” in Opere di Francesco Redi (Naples: A spese di R. Gessari, nella stamperia di A. Carfora, 1740–1741).

(17.) Knoefel, Francesco Redi on Vipers, 3. The Italian original reads iterata, e reiterata esperienza.

(19.) In the debates about snake venom, the replication of other people’s experiments played hardly any role at first. It became somewhat more important as the dispute with Charas unfolded, when—as readers of Leviathan and the Air-pump might expect—failed attempts at replication were at issue.

(20.) Knoefel, Francesco Redi on Vipers, 30. The Italian expression is per esperienze molte vole fatta.

(21.) Ibid., 6.

(23.) Redi, Experiments on the Generation of Insects, 70–71Emily C. Parke, “Flies from Meat and Wasps from Trees: Reevaluating Francesco Redi’s Spontaneous Generation Experiments,” Studies in History and Philosophy of Biological and Biomedical Sciences 45 (2014): 34–42.

(27.) Ibid., 6.

(28.) Ibid., 6.

(29.) Marco Aurelio Severino was the author of the work Vipera Pythia. Id est de viperae natura, veneno, medicina demonstrationes et experimenta nova (Padua, Italy: 1651).

(31.) Ibid., 9–10.

(33.) Ibid., 21.

(34.) Moyse Charas, New Experiments Upon Vipers. Containing Also an Exact Description of All the Parts of a Viper, the Seat of Its Poyson, and the Several Effects Thereof, Together with the Exquisite Remedies, That by the Skilful May Be Drawn from Vipers, as Well for the Cure of Their Bitings, as for That of Other Maladies. Originally Written in French. Now Rendred English. (London: Printed by T. N. for J. Martyn, 1670).

(35.) Another disagreement between the two researchers concerned the anatomical structure and location of the salivary glands of the viper. I will not examine this dispute here.

(37.) In his later work, Charas explicitly referred to van Helmont’s theory of disease.

(38.) Charas also spent some time in England, but only after his dispute with Redi. For biographical details, see Patrizia Catellani and Renzo Console, “Moyse Charas, Francesco Redi, the Viper and the Royal Society of London,” Pharmaceutical Historian: Newsletter of the British Society for the History of Pharmacy (2004): 2–10; for information about his works, see also Marie Phisalix, “Moyse Charas et les vipères au Jardin du Roy,” Archives du Muséum d’Histoire Naturelle 12 (1935): 469–72.

(40.) Ibid., 103.

(41.) Ibid., 106.

(42.) Ibid., 94.

(43.) Ibid., 109–10.

(44.) Ibid., 107–8.

(45.) Ibid., 133–34.

(46.) Ibid., 98.

(47.) Charas explained in detail: “We judged, that the vexed spirits unable to penetrate into the body, defended by the Theriaque, had wrought upon the outward part, and round about the place bitten, where they had coagulated the bloud, and caused the lividness; whereas the like spirits, having met with no resistance in the other Pigeon, had gained and wrought upon the inner parts, having left and as (p.242) ’twere despised the place, at which they were entred. We also wondred not, that the Theriaque, which had vigorously repulsed the Spirits introduc’d by the first bite, could not resist the latter but for half an hour, and that at last it was forced to yield, in regard that the number of the enemies was great, and being weakn’d by the conflict, it had but now endured, had not force enough to bear up against the new assault of the latter”; Charas, New Experiments Upon Vipers, 98–99.

(49.) Ibid., 116.

(50.) Ibid., 108.

(51.) Ibid., 117.

(52.) Novum OrganumFrancis Bacon, The New Organon (Cambridge, UK: Cambridge University Press, 2000), 159.chapters 7 and 8

(53.) Domenico Bertoloni Meli, “A Lofty Mountain, Putrefying Flesh, Styptic Water, and Germinating Seeds,” in The Accademia Del Cimento and Its European Context, ed. Marco Beretta, Antonio Clericuzio, and Larry Principe (Sagamore Beach, MA: Science History Publications, 2009), 121–34.

(54.) Quoted in Michael McVaugh, “The ‘Experience-Based Medicine’ of the Thirteenth Century,” in Evidence and Interpretation in Studies on Early Science and Medicine, ed. Edith Sylla and William R. Newman (Leiden: Brill, 2009), 112. In his essay on viper venom, Charas did not explicitly refer to Gordon’s work, but later he did refer to Gordon in his Pharmacopoeea; Moyse Charas, The Royal Pharmacopoeea, Galenical and Chymical According to the Practice of the Most Eminent and Learned Physitians of France: And Publish’d with Their Several Approbations (London: Printed for John Starkey at the Miter within Temple-Bar, and Moses Pitt at the Angel in St. Pauls Church-Yard, 1678).

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