SHiPS Resource Center
for Sociology, History and Philosophy in Science Teaching

Pasteur & Tyndall on Spontaneous Generation:
The Role of Biology Textbooks in Creating an Experimentum crucis

by James Strick

Who cannot have noticed in late years that some information media, by their condensed nature, feel pressured to distill complex debates into brief, sexy sound bites? One need only follow the television recap or morning-after coverage of a modern Presidential campaign debate to see this phenomenon in sharp relief. My argument here is that similar pressures are felt by those who write general biology textbooks.

Textbook writers face the need to: (a) present the history of as complex a subject as spontaneous generation controversies; as well as (b) carry out their function to inculcate stories of exemplary scientific practice into a young generation of potential future initiates. I suggest that these pressures were at work in the creation of the "textbook account" of spontan-eous generation controversies from about 1870 onward. This especially favored the selection of Louis Pasteur's swan-necked flasks and John Tyndall's dust-free chamber as icons, and the adoption of renderings of each of those experiments as an experimentum crucis. The conversion into iconic status was a long, slow process, however, that was not complete in English-language texts until the 1950s and 60s.

One might say that none of Felix Pouchet's or Henry Bastian's experiments favoring spontaneous generation succeeded in attaining experimentum crucis status most importantly because they lost. This seems however to transparently beg the question. Thus, I will show that at least some important writers at the time did not consider the experiments of Pasteur or Tyndall to be crucial or decisive, even one who did believe Bastian and Pouchet wrong about the germ theory. Furthermore, I will try to demonstrate the extent to which the historical portrayal of Pouchet and Bastian as "losers" had a great deal to do with the greater appeal and consequent propagation of the opposing experimentum crucis images. The result was that Pouchet and Bastian instead themselves became icons—of investigators who were biased a priori, experimentally incompetent, and irrationally obdurate.

I should emphasize at this point that this paper surveys primarily the English-language literature, and that this initial survey is admittedly preliminary and far from exhaustive. It is based on a hopefully representative sampling from the shelves of the Princeton University Library, of those texts which listed spontaneous generation as an index heading.

I. After the swan-necked flask experiments became famous in Paris, especially via Pasteur's Sorbonne lecture to the elite of Paris society in 1864, the response in British print was mixed at best. Thomas Huxley lauded the work in his Lectures to Working Men, while Gilbert Child, John Hughes Bennett and in America Jeffries Wyman were more skeptical of how much Pasteur had actually conclusively proven. Bennett and Child had criticized Pasteur on what was supposed to be one of his greatest strengths: microscopy. They pointed out that his low powers of magnification were shocking in the eyes of an up to date biologist or medical man, especially since Beale in Britain had made the use of higher powers in the study of bacteria widely known. This charge was picked up and repeated in vol. 3 of Richard Owen's respected Anatomy of the Vertebrates and in numerous journals such as the Lancet, British Medical Journal, and Popular Science Review.

Huxley's 1870 Presidential Address to the British Association for the Advancement of Science (BAAS), titled "Biogenesis and Abiogenesis," was absolutely seminal in changing this tone in the English-language literature on spontaneous generation. Abiogenesis was the term Huxley gave for spontaneous generation theories, and biogenesis the term he urged for the theory that living things could come only from other living things. Huxley made a strong case for Pasteur's experiments, and he singled out the swan-necked flasks as one of three setups whose results were particularly conclusive. Furthermore, it is important also to recall how absolutely seminal were Huxley's efforts in the 1870s to redesign biology education, including directly teaching a sample course to hundreds of British schoolmasters. Since this talk of Huxley's has been very widely cited and was used as one basis for his extremely influential course in Elementary Biology, this one reference to the swan-necked flasks may have been the single most influential one in disseminating their reputation as an experimentum crucis in the English-speaking world, especially in a form which was to be picked up by biology textbooks. The BSCS textbooks of the 1960s and 70s for instance, used Huxley's version of the history of the spontaneous generation debate (taken from Pasteur)—i.e., the lineage of Redi, Spallanzani, Schultze and Schwann, Schröder and von Dusch, Pasteur. It is important to recall that the success of Huxley's Elementary Biology course predates by at least ten years the financial successes achieved by Pasteur for the applications (e.g., vaccines) of his micro-biological theories and the competition for prestige that arose between labs as bacteriology as a discipline emerged. Thus, the impetus supplied by those successes for the exalting of the spontaneous generation story into a disciplinary founding myth only added on to a process already underway over the "founding" of biology—a discipline whose clear identity with recognizably modern outlines also emerged just prior to bacteriology; and which would also come to take the spontaneous-generation-slaying myth as a critical episode in the story of its own founding.

Phil Pauly, Jane Maienschein and others have shown that in America, by contrast, the emergence of biology as a coherent discipline took until the late 1890s in the universities, and that the emergence of the high school biology course did not occur until 1900-1920. In this country Woods Hole and the elite universities such as Harvard, Johns Hopkins and University of Chicago served as the point from which the concept of "general biology" was disseminated, comparable to Huxley's South Kensington course in Britain over 20 years earlier. And even on the British scene, Caron has shown that the general biology agenda pushed forward by Huxley's lieutenants stalled significantly in the 1890s, so that the appearance of many general biology texts was by no means a straightforward process.

Incidentally, Huxley's term "biogenesis" (for his viewpoint, as opposed to "abiogenesis" for spontaneous generation) was also a particularly appealing sound-bite picked up by many future biology textbooks, and indeed by practicing biologists as well. Note that his distinction of "Xenogenesis" (for what Bastian and most others called heterogenesis) did not seem to catch on, however. I would suggest that this is because the more simplistic opposed duality of Biogen/Abiogenesis lent itself better to the condensed sound-bite version of the story required for the limited space in a biology text. Even a recent New York Times "Science Times" piece discussed the topic "abiogenesis" as if the concept had always been known by that name. This is helpful, since in this study it can be at least provisionally assumed that a version of the story which uses Huxley's terms was probably derived from his account or its successors.

Given this, it is more than a little ironic that Huxley had hijacked the term "biogenesis" from Bastian, who was using it up until that time to mean exactly the opposite (i.e., spontaneous generation)! This must surely rank high in the litany of rhetorical coups pulled off by Huxley, in which defining the terms of the debate and making his terms stick was the single most effective stroke that guaranteed him victory. Indeed, we must credit him in this case with more than even his usual degree of rhetorical skill: the fact that this term is often listed as among those coined by Huxley himself reveals how much more completely than usual he managed to deny his opponent the rhetorical high ground, taking the opponent's own terms away and giving them opposite meaning which eventually stuck in the history books, and more importantly, in the biology books, when those began to appear.

II. Interestingly enough, despite the popularity of Huxley's BAAS lecture, even at the time, at least a generation was required before his arguments began to spread in textbooks. Figure 1 below shows this transition. It also shows that the conversion of spontaneous generation to icon status in textbooks occurred after the disciplines of biology and bacteriology attained some degree of stable identity, at which point
Figure 1. The fate of spontaneous generation in sample textbooks after 1870. Discussion became coupled with diagrams, while Pasteur's swan-necked flask (bars onleft) fared better than Tyndall's dust-free box (right).
textbooks multiplied and a founding myth became more appropriate. Note the sudden increase, in the wake of the BSCS and other post-Sputnik biology curricula, of the incorporation of Huxley's version of the story.

At the time just after the debates, Letourneau's 1878 biology text offered many strong arguments in favor of Pouchet's work on heterogenesis, especially that it supported the theory of evolution, but did not even mention the existence of Pasteur, let alone any experiments by him. Letourneau began a campaign to promote one of Pouchet's demonstration experiments to the status others urged for the swan-necked flasks.

An even more striking example of the absence of the symbolic experiments, which were later to be presented as if they had been all-determining at the time, is Klein's 1885 textbook on Micro-organisms and Disease. Though Klein takes the germ theory of disease as proven, in a discussion several pages long on heat-resistant bacterial spores in, e.g., the hay bacillus B. subtilis, he never even mentioned Tyndall, or his dust-free chamber, in the discovery of those spores. Furthermore, Klein, who knew Tyndall, declared that ten minutes' boiling was sufficient to kill spores, not even mentioning Tyndall's supposedly crucial discovery of the need for fractional sterilization. This is a statement with which Bastian and Burdon Sanderson would probably agree, but to which Tyndall and Huxley would be violently opposed. Indeed, in Tyndall and Huxley's construction of the victory of the germ theory over spontaneous generation, this discovery of Tyndall's was the decisive blow. Not until Bulloch's text of 1938 does this version come to clearly dominate, though by the late 1920s it was becoming more popular (see figures).

Huxley and Martin's Elementary Biology text, by contrast, made a claim which stretched the facts extraordinarily in the other direction from Klein, suggesting a felt need to still respond to the campaign in favor of spontaneous generation as late as the 1888 second edition. There they stated that "All forms of bacteria ... are found to produce resting spores." This was neither accepted by bacteriologists then or now. Only a few species, predominantly those of today's genera Bacillus and Clostridium, are capable of this, and even in the earliest days of bacteriology, such a sympathetic supporter as Huxley protege E. Ray Lankester was claiming that only B. subtilis and B. anthracis could produce spores.

Once the Huxley version of the controversy had been promulgated by Bulloch's 1938 book, however, a crucial threshold had been passed. Bulloch has been so widely cited and directly borrowed from for subsequent textbooks in microbiology and biology, that the account of Pasteur and Tyndall and the iconic images themselves spread much more rapidly from 1938 on. Oparin's influential 1938 book, The Origin of Life, even more widely read in a mass-distributed Dover Reprint of 1953, told similar stories on Pasteur and Tyndall, no doubt reinforcing the effect. However, and this seems quite important, from the 1930s on, as the iconic images began to spread in textbooks, they seem less and less to be about trying to convince anybody of anything about spontaneous generation, and more and more about serving as samples of exemplary scientific practice.

Oparin was an important source for the BSCS post-Sputnik biology curriculum mentioned above, as were James Bryant Conant's Harvard Case Histories. It is from Oparin's historically muddled account that later claims derived, that a simple dichotomy existed, including spontaneous generation and vitalism invariably linked on one side and biogenesis and mechanism on the other. Surely another important impetus in the sudden rise in textbook accounts of origin of life controversies was the 1953 Urey-Miller experiment and the late 50s involvement of big government funding, via NASA, in origin of life research. The Urey-Miller flask with electrode "ligthning flashes" very quickly became a textbook icon at this time. It has gone on to become as widespread or even more so, than the swan-necked flasks.

III. Holmes and Olesko have shown that, in the textbook use of Helmholtz's nerve propagation experiments, the presentation of the results in visual form was much more compelling. Similarly, it has often been remarked that the simplicity of the logic built visually into the diagram of the swan-necked flask is the secret behind its compelling appeal. I would argue that this overlooks another whole layer of the genius of this experiment. One of the statements most often repeated about Pasteur's and Tyndall's experiments by those texts which did pick them up in iconic form, is how remarkable it is that some of these swan-necked flasks and tubes of infusion can still be viewed today, in Paris and in London, all these decades later, as pure and limpid as they were when originally cooled after boiling. (Indeed, initially some textbooks were more likely to include actual photographs of such artifacts along with, or even in preference to, a mere schematic diagram of the flasks). This began at the latest with the 1932 Man and Microbes. It is no small feature of why these objects lend themselves to conversion into icons of science, that they remain, like bottles of fine wine, unchanged by passing time and thus lend themselves to display as museum objects in the Louvre or the Royal Institution in London. Clearly, Bastian's tubes of putrefied urine and Pouchet's of rotten hay infusion do not lend themselves to such a use. Changing and showing swarming microbial life was the very essence of how such a single tube could be claimed to disprove the evidence of a hundred tubes in which no growth occurred, in spontaneous generation debates. However, that very nature also made the tubes transient and aesthetically unappealing both in the debates at the time, and as potential museum items, an important strike against conversion to an icon in print. The fanfare which greeted the re-discovery of some of Tyndall's tubes in the early 1960s in a dusty closet of the physicist's old summer house in Switzerland gives testimony to the durability, if not immortality, of such status, once attained.

IV. On a separate, but related issue, John Hughes Bennett's support for spontaneous generation was linked to his "molecular theory" of cell formation, related to the cytoblastema theory of Schleiden and Schwann. Bennett was a longtime opponent of Virchow in many different quarrels, especially his claim that Virchow's famous statement of omnis cellula e cellula was a dogmatic pronouncement contradicted by Bennett's own observations. The spontaneous generation controversy was still raging at its peak in Britain at the time of Hughes Bennett's death in 1875, and it may well be his unbroken opposition to both Virchow and Pasteur which first led to their work in such widely differing fields being considered intimately connected in biology textbooks. Virchow himself had begun a campaign by shortly after Bennett's death to discredit the former-majority belief (originally including himself) in Schleiden and Schwann's cytoblastema theory, by now arguing that one of the greatest problems with that view was precisely that it left the door open for, indeed even implied, spontaneous generation of cells. This was an active historical reconstruction by Virchow, highlighted by the fact that almost all British cytoblastemists, as well as Schwann himself, were up until 1868 ardent opponents of spontaneous generation, so that it may be inferred they saw no such implication in a cytoblastemic theory of the origin of cells.

The misperception that, during the 1850s and up until 1870 or so, most British scientists perceived Virchow's arguments about cell-theory to be relevant to the spontaneous generation debate, is also dispelled by this analysis. An 1868 paper by Bennett, in favor of heterogenesis, seems to have been uniquely important in creating the linkage between the two discourses in British science. And even then, the leading advocate who emerged in Britain for spontaneous generation, Bastian, did not dwell much on this point, preferring to focus on the origin of bacteria and what Bennett would have called histolytic molecules. Yet Virchow's linkage of 1877 has persisted in biology textbooks because of the success of his slogan, and thus, of his right to be considered authoritative historian. And as a result, the important role played by Bennett's theory has faded into obscurity, as has the consensus of ideas it helped consolidate, which produced a period from 1868 until 1875 or so in which Listerian surgical claims were viewed with great skepticism, and spontaneous generation theories could seem reasonable even in the British context.

Conclusion

Neither the swan-necked flask nor dust-free box experiments were viewed as crucial experiments by numerous authors well after the supposed final defeat of spontaneous genera-tion, into at least the 1880s. The visual images of these experiments took in fact well over 50 years to begin to become established in textbooks, in a process bound up in complex ways with the evolving disciplinary identity of "biology" and "bacteriology" or "microbiology." However, once this occurred, these iconic images (usually tied to Huxley's 1870 version of the spontaneous generation story and his "biogenesis/ abiogenesis" dichotomy) began to be copied rapidly from one text to another because of their textbook-suitable properties. One of the most outstanding properties was their visual appeal, which allowed them to stand as much (or more) as examples of good scientific thinking embodied in experimental design as they stood for proof against advocates of spontaneous generation.

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