Louis Joblot and disproving spontaneous generation of animalcules

Although in 1718 it gave rise to the first French treatise of microscopical research, the work of Louis Joblot (1645-1723), published in Paris with the title Descriptions et usages de plusieurs nouveaux microscopes, tant simples que composés was seldom discussed by historians. Historiography for Joblot is both poor and dated, especially if compared with historiography for Leeuwenhoek and Malpighi. In 1895, Konarski claimed a pre-eminent place for Joblot in the history of protozoology, attesting that he had described many animalcules not previously observed, and had discovered their contractile vacuole. Oudemans later showed that Joblot also described the parasitic nymph of the pond Mussel.¹⁵⁹ However, the biographer of Leeuwenhoek, Clifford Dobell strongly defended Leeuwenhoek’s primacy going as far as to consider that Joblot had imitated him.¹⁶⁰ Joblot’s book was ignored by Jacques Roger, who, in 1963, integrated him into the context of the growing quarrel of animalculism against

ovism.¹⁶¹ According to Roger, Joblot showed the spermatic animalcules^g to some Italian and French physicians. Most likely, Roger has found evidence for this but did not quote his sources, and actually such interest in spermatic animalcules does not stem at all from the 1718 treatise. Nowhere is there mention of the spermatic animalcules.

Even the term “animalcule” is absent; Joblot always uses “animals”, “fishes” and sometimes “insects” to name the animalcules of infusions^g. Van der Pas in his

biographical entry for Joblot, in DSB, and more recently Fournier, have driven attention

159 Oudemans is cited by Van der Pas 1973, 110-111.

160 Dobell 1932, 372.

161 Roger 1993, 312-313.

to Joblot’s antispontaneist experiments.¹⁶² Descriptions et usages de plusieurs

nouveaux microscopes sanctioned 38 years of microscopical research. Joblot’s interest in microscopic beings dates back to 1680,¹⁶³ two years after the demonstration of the animalcules given before the Académie des sciences by Christiaan Huygens (1629-1695) and Nicolaas Hartsoeker (1656-1725) during the summer of 1678.¹⁶⁴ The observations and experiments on animalcules, which are reported in the book, were carried out mainly between 1710 and 1716, as shown by mention of the dates of the observations. The book, which was accepted in 1716 for printing by the Académie de sculpture et de peinture, of which Joblot had been professor of mathematics since 1699, is divided into two parts, first the construction of microscopes and second the study of microscopical beings, mainly animalcule. The second part of the book, which I will mainly deal with here, is organised around a central thematic --the refutation of spontaneous generation with experiments and arguments-- to which many detailed descriptions and references to the plates of the animals of infusions served as a counterpoint, being good example of “microscopical report”. Up to but excluding Konarski (1895) and three pages by Fournier, secondary literature does not supply a comprehensive account of Joblot’s book and experiments, and therefore I will analyse it in detail in the following pages before presenting its reception in the eighteenth-century.

Joblot’s journal of experiments guided the chronological structure of the second part of the book, in the middle of which the antispontaneist “hypothesis” is interpolated. He first reports experiments during the 1680s and 1710s on the life and death of eels of vinegar (pp. 2-12), followed by the animals appearing in the pepper infusion as demonstrated by Hartsoeker when in Paris in 1678 (12-16). Joblot then describes animals from various infusions as observed between July 1710 and Autumn 1711

162 Fournier 1991, 182-183; Van der Pas 1973, 110-111.

163 Joblot 1718 II, 2, 5.

164 Joblot 1718 II, 12-13. See Ruestow 1996, 25-26; Van der Pas 1973, 110; Cole 1926. The 30th of July 1678, Huygens demonstrated not only the animalcules of the pepper infusion, but also “a infinity of small animals similar to the small frogs when they form. They were in spermate canis’ (PV AS 1675-1679, f° 185-185v). Both observations were reported in Huygens 1730, 608-609. On the quarrel that followed, see Roger 1993, 302-304.

39), that led to the crucial experiments on the infusion of hay carried out in October 1711 (39-40). From then on comes an interruption because Joblot stopped reporting directly to his journal, and began synthesising previous empirical data for the repetition of which he gave much advice (40-43). The three following pages (44-46) disclose what he calls his hypothesis or conjecture on the generation of the small animals. The next forty pages continue with many descriptions of new animals from other infusions (46-85), which brings the journal to December 1718. Finishing with the microscopical reports, the book then comes to a close with a dissertation of ten pages long on optical perception through the microscope. The observation seem to have been interrupted between 1680 and 1710. But Joblot stated that he carried out his observations over 36 years (he wrote the passage in 1716).¹⁶⁵ Two pieces of evidence show that he indeed continued the microscopical observations during that time. Guillaume Amontons, who brought him vinegar containing many eels for observation, died in 1705 and was active in the Académie des sciences between 1687 and 1705. Joblot also reports he made observations on the metamorphosis of a worm in 1692 and 1693.¹⁶⁶

In which way were the animals described by Joblot? He certainly did not use routine methods as in the Renaissance treatises on botany, where authors filled up several entries in a fixed order: names, morphology, generation, costums, etc. Yet Joblot’s approach remains category-specific, though without using a rigid order adopted for the description of the animal. He is much more attracted by some “remarkable phenomena”

presented by an animalcule, which leads him, on the contrary, to neglect reporting on some animalcules considered too common. Thus no systematic approach was used.

Nevertheless, categories are meaningful both for the information displayed about animalcules --that will promote Joblot as the leading discoverer of infusoria until 1786¹⁶⁷-- and because these categories reveal things about the context to which he belonged. He indeed scrutinized morphological aspects of animalcules, always trying to

165 Joblot 1718 II, 5.

166 Joblot 1718 I, 34-36.

167 See chapter 8.4.3.

put the right name to the right shape --a fully diagnostic^g scheme-- and named them as oval, sock, kidney, slug, swan, turtle, etc. Still Joblot, as Leeuwenhoek, Huygens or, later Eichhorn or Colombo, did not use a systematical report, and paid no attention to names, despite what has been said by historians.¹⁶⁸ Anatomical observations also became morphological analysis, when he identified eggs, heart and intestine in several animals. Reasoning still plays an important part in his work; for instance he deduced that many of the animals should have eyes since they were able to avoid each other when swimming.¹⁶⁹ Altogether, there are about one hundred experiments --most of these vegetable infusions-- conducted over six years, that yielded between thirty and forty species described and engraved (plate AA), for which Joblot gave further details on their morphology, behaviour, and, less important, on their anatomo-physiology.

Death of the infusion animals and the determination of their limits is a recurrent theme in the works. He noted for many animals the standard duration of their life, their morphological changes after death¹⁷⁰ and started investigating the various causes of death, such as putting a drop of vinegar in an infusion or in oysters, a procedure also used to confirm the specificity of some new kinds of eels, appearing in the infusion of carnation.¹⁷¹ Joblot determined that certain animals could only live in a range of various degrees of warmth and cold.¹⁷² Similar techniques were used previously notably by Leeuwenhoek and Power.¹⁷³ Attention was also paid to other dimensions related to the

“circumstances of the observation”, like the smell of the infusions, and to more

168 Stafford 1997, 233. See chapter 8.

169 Joblot 1718 II, 5, 33, 61, 70.

170 Joblot 1718 II, 34, 61.

171 Joblot 1718 II, 6, 18, 22, 28-29.

172 Joblot 1718 II, 19: “There is thus a certain degree of warmth that keeps them alive and another a bit higher which kills them.” See also ibid. II, 15-16.

173 See Wilson 1995, 86; Fournier 1991, 182.

measurable variables such as time, motion, quantity of animalcules and temperature.

Time is most likely the better heeded variable along the whole book. Joblot usually reported dates, hours and duration of the observations, life span of the various species,

of the infusions, succession among time of various species in the same infusion, and the experimental time used in the procedures. He recorded for instance having boiled an infusion over a quarter of an hour. Joblot frequently kept infusions for more than one year, observing the kinds of animals that succeeded in it.¹⁷⁴ Equally strong attention was given to types of motion of the animals, usually well described and determined by means of idioms, sometimes even compared to the much richer show of dancers.¹⁷⁵ One of the “behavioural motions” is of course mating, which Joblot acknowledged and engraved for many species. He illustrated --with a much more precise technique than Leeuwenhoek used for bacteria¹⁷⁶-- through dotted lines starting from the centre of the animals (we now identify as bacteria) the various sorts of their motions (Fig. A pl. 2).

He also detected the alternation of several types of gyratory and straight motions in some animals he made engravings of, with an iconographic technique similar to that used to represent the lines of force in magnets (Fig. A Pl. 2, animal Q, and O).¹⁷⁷ A close technique of dotted circling allows the delineation of effects of the little whirlpool by which some “aquatic caterpillars” (Rotifer^g) draw smaller animalcules in their mouth (Fig. B pl. 6).¹⁷⁸ The same methods will be used later by German scholars in the second part of the century to represent the motion of the lips in some Rotifers and Ciliograda, and the motion of animalcules (Fig. C).¹⁷⁹ For Joblot, such an interest in the various aspects of motion and in its representation probably arose from his professional environment, as well as from his personal interests. He indeed invented the first artificial magnet, and was a professor of geometry at the Paris Academy of Arts. Yet motion is not only referred to for the charm of its “show”--animalcules move “like

174 Joblot 1718 II, 15-16, 20.

175 Joblot 1718 II, 35, 50, 56.

176 See Dobell (1932, pl. 24) for the motion of the bacteria b. Leeuwenhoek illustrated it in a letter of the 17th September 1683.

177 Joblot 1718 II, 13-14; see also ibid. II, 64-65.

178 Joblot 1718 II, 54-55. A is the mouth of the animal.

179 Rösel von Rosenhoef 1755, 593, pl. 95, Ledermüller 1763, pl. 48, 50, 88, Gleichen 1778, pl. 14 to 28.

dancers”-- because the kind of motion also served as a mark enabling one to distinguish among two species of eels.¹⁸⁰

180 Joblot 1718 II, 29.

Joblot’s book represents a good example of the systematic rationalisation that was obtainable using microscopy in the beginning of the eighteenth-century. Such a rationalisation is evident in his interest in developing five topics: 1. explaining optics and the construction of microscopes; 2. doing research on the microscope itself; 3.

giving the measures of the focusing powers used in the observations; 4. explaining general procedures enabling one to use the microscope and to conserve animals alive; 5.

supplying readers with good narrative descriptions of the observations allowing their reproduction. I leave the three first points for discussing in chapter four and develop the latter two here.

On several occasions, and contrary to Leeuwenhoek, Joblot indeed showed how to use the various kinds of microscopes and explained the many fine operations necessary for accurate observations: dipping the point of a feather in the infusion to take a drop, using a pipette, handling several kinds of tweezers, sticking the glasses of the slide with gum water, nailing insects to cardboard, blowing sand to stick it to the glass, fitting tadpoles and small lampreys within a glass tube, setting the glass tube to the microscope, using a

filter for the infusion, etc.¹⁸¹ Each of these procedures conforms to the general scheme of showing secrets of the microscope developed by Joblot, which was furthermore

181 Joblot 1718 I, 8, 74-78; ibid. II, 43, 62-63.

integrated to the ideology of utility and relative transparency defended in the academic milieu of Paris, including the creation of a Société des Arts in the 1720s.¹⁸² Many tools, like the pipette, the tweezers, the glass-tubes and the “animalcule conveyor”, are also shown in engravings (Fig. D pl. 3, 7 and 10).¹⁸³ The value of these procedures is two-pronged, being on the one hand the right way to make a successful observation, and on the other hand, on the level of communication, they fully belonged to the social

environment. Such a social factor appears to have been very important to Joblot, for he often reported having done an experiment in collaboration with an anonymous

someone, discussed with someone else or demonstrated the “show” of the animals to

“several persons”. People who saw the eels of vinegar^g through the microscope at the turn of the century in Paris stopped eating salad, and Joblot strove to convince them the creatures were so small as to be innocuous. As an honnête homme he was delighted to

“answer the difficulties [the spectator] would have honoured me to propose on what he was seeing [through the microscope]”.¹⁸⁴ Observations were sometimes made with “a person of the higher ranking”. In other cases, some friends also made the infusions by themselves, and Joblot notified the public of their results. On several occasions, he defended a kind of moral value he imputed to the show depicted through the screen of the microscope, as being far more estimable than those showed in comedy, opera, dancing and “fights of animals of that magnificent City”.¹⁸⁵

Joblot, however, was also pragmatic and on repeated occasions invited people to repeat experiments in order to see the “spectacle” and to be convinced of it by themselves.

Nothing beats empiricism: “I feel obliged”, said Joblot, “to warn that a written

explanation, however long it is, will never supply full understanding, one must have to manage in using all the pieces of this microscope [universal], and to prepare the objects one can observe through it. In less than two hours of conversation with someone well

182 On utility in the Académie des Sciences, see Daston & Park 1998, 353-354, Licoppe 1996, 116-124; Briggs 1991. On Société des arts, see Hahn 1971, 109-110.

183 Joblot 1718 I, 7, 16, 58-60; ibid. II, 18-19, 60.

184 Joblot 1718 II, 62.

185 Joblot 1718 II, 56.

acquainted with such an understanding, one will learn more than what he would get in eight days of reading (...) Which is the reason why I will say only necessary things as to avoid boring people”.¹⁸⁶ This is saying that the transmission of knowledge always has other resources than writings, this being a current belief in Joblot’s academic

environment. Consistent with such a demand for conciseness, Joblot clearly outlined the way to make infusions, with cold or hot water, and unfurled before the reader’s eyes a whole education of seeing: how to observe, what to observe and what means could be used to refine the conditions of vision. He disclosed, for instance, suitable means for avoiding opacity of the infusions, and demonstrated how to take advantage of the natural conditions, such as waiting for a drop to start drying in order to slow down the motion of an animal in order to observe it better.¹⁸⁷ He equally gave many indications on the life span of small animals according to the seasons, and illustrated the means for conserving live animals by showing which were their normal living environments.¹⁸⁸ All these details, written with conciseness, aim at allowing others to reproduce

observations, and are important clues in accounting for the rationalisation of his way of managing microscopy.

It would not be misleading to say that the major goal of Joblot’s book is the

experimental and argued rejection of spontaneous generation. Joblot committed himself as an antispontaneist from the first pages of his avertissement: “I added to my

observations some conjectures on the production of the various species of small animals which appear in the infusions. I cannot belong to the party of those who ascribe it to putrefaction”.¹⁸⁹ In order for his reader to fully understand the hypothesis, Joblot also took the precaution of progressively introducing, throughout the book, the experimental means suitable for the rejection of spontaneism. Parts of the major experiment, paired with their theoretical meaning, appeared separately and were set at the beginning of the

186 Joblot 1718 I, 59.

187 Joblot 1718 II, 62-63. Similar procedures will be used by Trembley 1747, 636-637 and by Hill 1752a, 97.

188 Joblot 1718 I, 16, 78; ibid. II, 5.

189 Joblot 1718 I, avertissement.

book (second part): comparison of two jars, corked and uncorked, with cold vinegar to test the generation of eels,¹⁹⁰ procedure of heating the vinegar that results in killing the small eels it previously contained. In a sense, the various aspects were settled there one by one, to prepare for full understanding of the major experiment, a play enacted in the middle of the book and immediately followed by the interpretation. Hence Joblot attacked spontaneous generation through “experiment and reasoning”, but also using a harmonious and somewhat aesthetic strategy of organising the information. Two experiments were thus carried out starting on 4th October 1711. He made two cold infusions of hay in separate jars, of which one was accurately corked, the other left open. Two days after he observed three sorts of animals in both infusions, and deduced an argument in line both with the hypothesis and the phenomena observed: “this experiment seems likely to persuade that these animals were produced by eggs that other animals had laid on this hay, and not produced by those which were spread in the air”.¹⁹¹

The original experiments testing the spontaneous generation of animalcules must be ascribed to Christiaan Huygens. In 1679 Huygens carried out experiments with cold corked and uncorked infusions of pepper, of which he acknowledged that both infusions generated animalcules after ten days.¹⁹² Yet he considered that it disproved spontaneous generation, maintaining that “all these animals come from outside or (from eggs) of the animals that float in the air coming to these putrid waters”.¹⁹³ A year later, in 1680, a similar experiment was performed by Leeuwenhoek with an infusion of hay --likely the same year as the experiment performed by Joblot on eels of vinegar¹⁹⁴-- and published in 1683 in Philosophical Transactions, while those by Huygens were issued

posthumously, in his 1703 Dioptrica.¹⁹⁵ Leeuwenhoek’s publication was the base for

190 Joblot 1718 II, 5-9.

191 Joblot 1718 II, 39.

192 Fournier 1981, 205.

193 The Dioptrics from Huygens is quoted by Fournier 1981, 205.

194 Joblot 1718 II, 2.

195 Fournier 1981, 204.

Dobell and Fournier’s claims that Joblot imitated Leeuwenhoek and Huygens, a point I will progressively disprove by showing that, on the contrary, Joblot’s two experiments, synthesised into an experimental system, brought a rationalised solution that crowned the antispontaneist line of works, started with the experiments by the physician Francesco Redi (1626-1698).¹⁹⁶ However, attention to the differences between

Leeuwenhoek and Joblot’s styles of experimenting already allows shifting of the issue from imitation to rationalisation. Consequences of this experiment as underlined by Joblot show that the two frameworks are totally different. Leeuwenhoek indeed wanted to provide evidence against spontaneous generation of animalcules and imagined the very same experiment as Huygens. But Leeuwenhoek did not at first succeed in his experiment, and he later started to engage himself in a personal campaign against spontaneous generation, without having strong empirical data in hand to uphold his position, which Ruestow interpreted as a claim for social recognition.¹⁹⁷ I dare say that Leeuwenhoek did not manage to grasp the precise theoretical limitations conveyed by the experiment he had carried out. In other words, Leeuwenhoek did not comprehend the meaning of his own experiment, and consequently could not satisfy in this respect his microscopical and related social acts with an empirical rationale. Quite on the

Leeuwenhoek and Joblot’s styles of experimenting already allows shifting of the issue from imitation to rationalisation. Consequences of this experiment as underlined by Joblot show that the two frameworks are totally different. Leeuwenhoek indeed wanted to provide evidence against spontaneous generation of animalcules and imagined the very same experiment as Huygens. But Leeuwenhoek did not at first succeed in his experiment, and he later started to engage himself in a personal campaign against spontaneous generation, without having strong empirical data in hand to uphold his position, which Ruestow interpreted as a claim for social recognition.¹⁹⁷ I dare say that Leeuwenhoek did not manage to grasp the precise theoretical limitations conveyed by the experiment he had carried out. In other words, Leeuwenhoek did not comprehend the meaning of his own experiment, and consequently could not satisfy in this respect his microscopical and related social acts with an empirical rationale. Quite on the