[Addendum, September 10th: in looking at the full text of the letter referenced below, indeed Bidlow did NOT use a Spinoza microscope, but was only referencing Kerckring’s use as well as his observations on the limitations of the microscope. I keep the post up though, to preserve the thought process of a deadend of research, for whatever that may be worth, as well as for the value of Bidloo’s citation of Spinoza at a near near the death of his friend Eric Walten: Govert Bidloo’s 1698 Refference to a Spinoza Microscope ]
Physician to the King and Another Spinoza Microscope?
[The arguments below I present prospectively, waiting for a confirmation of the source]
I stumbled upon some evidence that there is a second Spinoza microscope in the historical record, and it is my hope that this glass may bring to view more of the details for which I have been straining. Thus far, the only first hand report we have is from Spinoza’s fellow Latin student, and possible van den Enden disciple, Theodore Kerckring, who in his Spicilegium anatomicum (1670), describes how with Spinoza’s glass he had seen a “infinitely minute animalcules” teeming upon the viscera. This description is to be questioned, firstly, because Kerckring himself warns us a few sentences before, that all observations of microscopes have to be doubted; but also because Kerckring reported elsewhere some microscopic observations which plainly come from the imposition of fantasy upon sight.
In this case the account may be more sobering and exact, though I have yet been able to actually assess the content of the claim. The report comes apparently from Govert Bidloo, and man of fairly high standing, and apparently connections to Spinozist political movements of his day. In 1694 Bidloo was appointed professor of anatomy and medicine at the university of Leiden, a post to which he was not able to well-attend due to also becoming the personal physician to stadholder William III, who would die in his arms in 1702. If indeed Govert Bidloo did use and favor a Spinoza microscope, he was a well-connected anatomist and physician, and public champion of microscopic investigation.
Collaboration with van Leeuwenhoek: Parasitic Protozoon
The fact of Bidloo’s use of a Spinoza microscope is at this point circumspect, as for the moment I have only a summary of the mention of praise for a Spinoza microscope-glass (vergrootglass), in a memoir-letter written to the famed microscopist Antony van Leeuwenhoek, subsequently published in the same year, 1698. I do not read Dutch, so I had to rely upon the summation of a website owner to understand its content.
“Passage from a letter of Govard Bidloo (Henrik van Kroonevelt Ed., 1698, page 27) a memoir to Antonie van Leeuwenhoek, about the animals which are sometimes found in the liver of sheep, on the etiology of diseases (the Plague) and referring to remarks of scientists abroad on his work, and quoting the quality of the Magnifying glass made by Benedict de Spinoza.”
This is found here. The citation given, aside from the letter itself, is not traceable. Perhaps it is a television production:  “Cells of Spinoza”: Tetsuro Onuma, Representative of Yone Production Co.Ltd. (2002).
The phase “quoting the quality of the Magnifying glass” I assume probably means “citing the quality”. Because the context is missing for me, there is no way to affirm what I would suspect, that Bidloo is writing to van Leeuwenhoek about his observations of small parasites and their eggs, as found in the liver of sheep, and it is by virtue of the excellence of Spinoza’s glass that his observations are assured. This is somewhat also how Kerckring references his Spinoza microscope.
Historical Context For Bidloo’s Letter to Van Leeuwenhoek
Two decades before Bidloo presented his findings to van Leeuwenhoek, in 1674 van Leeuwenhoek was startling the world as he peeled away the curtain of the microscopic, revealing to a new level of exact description and illustration, a world of minute animals and structures. Under his tiny, spherical lenses the first bacteria and protozoans were coming to life, and he began letting the world know about in through letters written to leading scientists in London. And in October ’74, he wrote to the Royal Society about his discoveries of “globules” and “corpuscles” in the bile of domesticated animals, the first Sporozoa and parasitic protozoon. It would be as an expansion upon these observations that Bidloo would conduct his own microscopic examnations. I quote here from Dobell’s excellent book in van Leeuwenhoek to give a sense of the early material and Bidloo’s connection to it, first from the letter, and then from Dobell’s commentary:
…in the bile of suckling lambs there are very little globules, and some, though very few, bright particles. which are a bit bigger; besides irregular particles, of divers figures, and also composed of globules clumped together.
The bile of yearling sheep I find to be like that of suckling lambs, only with this difference, that in this bile there are also oval corpuscles of the bigness and figure of those I remarked in ox-bile. (Letter 7 to the Royal Society, October 19th 1674).
I think there can be no doubt that the “oval corpuscles” – called eijronde deeltgensin the original – which Leeuwenhoek discovered in the gall-bladder of one of his “three old rabbits,” were the oocysts of the coccidian Eimeria stiedae; while the comparable structures which he found in the bile of sheep and oxen were, equally certainly, the eggs of trematodes [Dobbell notes: Fasciola hepatica– the worm itself -was well known to L.; for the Dutch anatomist Bidloo (1649-1713) dedicated a little memoir to him, in 1698, in which it was described and figured. If my interpretations be correct, the foregoing extract records the first observations ever made upon the Sporozoa or upon any parasitic protozoon (200)
Antony van Leeuwenhoek and his ‘Little Animals’
Eggs and the Source of Disease
It is regarding these Fasiola hepatica that Bidloo is writing to van Leeuwenhoek in 1698, apparently part of a collaboration of observations between the two microscopists. This is how Frank Egerton sums up the correspondence in his article for the Bulletin for the Ecological Society of America :
Leeuwenhoek examined flatworms (flukes) from the livers of diseased sheep under a microscope and suspected that the sheep got the worms from drinking rainwater that collected in fields (21 February 1679, Leeuwenhoek 1939-1999, II:417-419). He pursued the subject no further until 1698, when he and Professor of Medicine Goderfridus Govard Bidloo (1649-1713) of Leiden University (van der Pas 1978) discussed liver flukes in sheep. Boththen wrote up their observations for publication, with Leeuwenhoek sending his to the Royal Society and Bidloo sending his to Leeuwenhoek, who had them published in Delft. Bidloo sent with his letter an overly precise drawing of a fluke, which shows two eyes, a heart, a circulatory system, and intestines that existed only in his imagination. Nevertheless, Bidloo did recognize the eggs and concluded correctly that the species is hermaphroditic. He also generalized from his observations that these worms seem to cause disease in sheep and that worms probably also cause disease in humans (Bidloo 1698, 1972). Leeuwenhoek went out and attempted to find fluke eggs in fields and ditches, where they might have been deposited in sheep feces (2 January 1700, 1939-1999, ?), but he had no way to identify them if he had found them. The fluke life cycle is so complex that it was not fully understood until the mid-1800s (Reinhard 1957). (53)
“A History of the Ecological Sciences, Part 19”
Indeed, the lifecycle of F. hepatica is quite complex, as it relies upon a symbiont aquatic snail, something no microscope would reveal to these men, but it is good to note that Bidloo’s microscope and analysis did properly identify the eggs of F. hepatica, something which may give clue to the magnification of his glass. It would appear that the two men were operating under at least remotely similar powers of glass, and at this point van Leeuwenhoek had achieved magnification really beyond compare for the century.
Bidloo's illustration of the flatworm F. hepatica
The size of the eggs in question may be in order. They come in the thousands, so together are visible to the naked eye, but the eggs themselves are microscopic, measuring approximately 130-160 µm, or 130/1000th of a millimeter:
According to their optical appearance and approximate measurements, we isolated about 1,300-1,500 ‘large’ eggs from a fairly large quantity of sheep faeces. Of these, 300 were measured and their average size was found to be 154 (143-180) x84 (75-102) µm. Fasciola eggs of normal size found in the faeces of the same sheep measured 129 (107-162)x 71 (61-79) µm.
“Unusually Large Eggs of a Fasciola hepatica Strain” (1982) D. Duwel
As I have not read Bidloo’s account, I as yet cannot tell if his glass resolved such detail, but van Leeuwenhoek’s description of “oval corpuscles” must have. And we should keep our mind open to this possibilities.
If we are to speculate, having identified what Bidloo saw and concluded, and assumed that he used a Spinoza made glass, what was the nature of Spinoza’s “vergrootglas”? Literally, this word means “magnifying glass”, something distinct from the word for microscope. It is the same word used to describe the instruments sold from Spinoza’s estate at auction on November 4th, 1677. (It is even conceivable that this was one of those instruments.) A vergrootglas could be anything from a swivel-armed spectacle glass used for dissection and study, to the very powerful simple, single-lens microscopes that Swammerdam and van Leeuwenhoek used. Aside from the more famous Leiden anatomists who used a simple microscope, we are told that Bidloo’s successor to the university position, Boerhaave, used a lens as small as a grain of sand (Ruestow 95). But the story is unclear. Bidloo was a student and friend to Ruysch, a fellow student and associate of Kerckring from ’61 onwards, who used magnification quite sparingly, and would have had no need of such an intense and difficult lens.
Devils and Parasites
There is another interesting point of about Bidloo’s biography which makes his 1698 reference to Spinoza’s lens more than a point of curiosity. It is twenty-one years after Spinoza’s death, but something more than simply the persistence of the efficacy of Spinoza’ instrument forces his name into consciousness. Bidloo, the physician of William III, was apparently a political activist of a sort, a champion of republican values. And just the year before his rather vociferousfriend Eric Walden had died in prison, perhaps by suicide following a series of failed suits for his freedom, under the general accusation of being a Spinozist-atheist. Walten’s escalating pamphleted attacks against the Dutch Reformed Church, in defense of Bathasar Berkker’s “The World Bewitch’d”, were fierce and reminiscent of Spinoza’s friend Koerbagh, who also died as a political prisoner. Berkker had maddened the religious in his Cartesian-like argument that because their could be not causal interaction between Spirit and Matter, devils and angels could have no effect on this world. This denial of both the miraculous and the diabolical enraged the pious, and when Walten wrote on Berkker’s behalf, the ire came to be directed towards him, eventually with legal consequence. This connection between Bidloo and Walten I find, thinly, but indicatively here:
In 1688 he took up the cause of William III against James II and showed himself to be a staunch defender of popular sovereignty and the elective nature of monarchy. Next, he turned to the question of the civil rights of governments over the church, and two local disputes, one concerning the privileges of the regents of Amsterdam, and other Rotterdam tax upheavals. [note, after “regents of Amsterdam”: It is unclear which pamphlets in this particular row were written by Walten and which by his friends Govert Bidloo and Romeijn de Hooghe, the famous engraver. See Knuttle, “Ericus Walten”, p. 359-383.] (44)
“Eric Walten (1663-1697): An Early Enlightenment Radical In the Dutch Republic”, by Wiep van Bunge, in Disguised and Overt Spinozism In and Around 1770
Whether Govert Bidloo used Spinoza’s microscope in his observations on the hepatica or not, I cannot say for certain now, but his reference in the published memoir, in the context of his observations on parasites of the body and a suspicion that they lead to human illness no doubt reflected to some degree the events that of the years previous, and the sourness of the death of Walten in prison. What comes to mind is Spinoza’s reflection to Oldenburg so many years before, that we are like a worm in the blood, how our perceptions are only most often local to what jostles us, itself a reflection on Kircher’s microscopic discovery of worms in the blood of plague victims. (Some thoughts here: A Worm in Cheese ). One must remember that this was not only a time of political and religious upheaval, but also a time of plague. The clearness of Spinoza’s glass no doubt, in the minds of his admirers, expressed the clarity with which the political body must be examined. Bidloo’s study of the bile of sheep, in search of parasites with Spinoza’s glass either in hand or in mind, surely struck him as fitting.