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Swammerdam, Jan


(b. Amsterdam, Netherlands, 12 February 1637; d. Amsterdam, 17 February 1680)


Swammerdam’s father, Jan Jacobszoon Swammerdam, son of a timber merchant, was an apothecary who in 1632 had married Baertje Jans Corvers. The couple’s first two children died in early childhood. In 1640 was born Jan’s brother, Jacobus, who became an apothecary, and in 1642 a sister, Jannetje. Jan’s mother died in 1661. His father had acquired some fame as a collector of curios, including minerals, coins, and animals from all over the world. As a boy, Jan helped care for this collection.

He matriculated in medicine at the University of Leiden on 11 October 1661. Jan’s own collection of insects impressed his schoolmates, including Regnier de Graaf, Frederik Ruysch, and Niels Stensen (Steno). Robertus Padtbrugge was a fellow student who later joined the East India Company and sent Swammerdam exotic animals. The eminent professors Franciscus dele Boë Sylvius and Johannes van Horne both refer in their publications to Swammerdam’s student researches. He qualified as a candidate in medicine in October 1663, and then spent some time in Saumur, France, staying with Tanaquil Faber, a professor of philology at the Protestant university there.

From about September 1664, Swammerdam lived in Paris as the guest of Melchisédech Thévenot. He was an active member, as was his friend Steno, of Thévenot’s scientific academy, an informal club that met to watch experiments and dispute over Cartesian ideas. Returning to Amsterdam about September 1665, Swammerdam joined a group of physicians calling themselves the Private College of Amsterdam, which included Gerhard Blaes (Blasius) and Matthew Slade. The group met irregularly until 1672 and published a description of their dissections. In the winter of 1666–1667, Swammerdam was again in Leiden, where he dissected insects and collaborated with van Horne on the anatomy of the uterus. His medical thesis on respiration, based largely on research carried out in 1663, earned him the M.D. on 22 February 1667. There is no evidence of his ever settling into a medical practice,1 although in 1670 he was granted the privilege of dissecting bodies in Amsterdam, and he does allude once to being kept from his research by the demands of the seriously ill.2

Driven by an inner passion and encouraged by Thévenot and other friends, Swammerdam devoted his life to scientific investigation, but he was interrupted by illness, by his father’s insistence that he earn a living, and by periods of depression and religious anxiety. He stayed for a time at The Hague, perhaps as a guest of Maurice, prince of Nassau, who had fishermen bring him specimens, and he occasionally visited Leeuwenhoek in Delft.3 He lived during the summer of 1670 in the village of Sloten, just outside Amsterdam, where he studied mayflies.

The mystical prophetess Antoinette Bourignon was accompanied in her exile by a friend of Swammerdam’s. Jan wrote to her for spiritual comfort on 29 April 1674, and asked her permission before publishing his researches on the mayfly. He visited her in Schelewig–Holstein, between September 1675 and June 1676. On 18 July 1675 Steno sent Swammerdam’s drawings of silkworm anatomy to Malpighi, reporting that the author had destroyed the manuscript text and that they should pray for their friend in his search for God.4 But Swammerdam’s rejection of science was not final, for in January 1680 he provided in his will for the publication of his manuscripts, and these give evidence of having been revised in the last year or two of his life. Not until a half century had passed, however, were his wishes carried out; Boerhaave published the Biblia naturae in 1737–1738.

Swammerdam’s biological researches fall into two distinct categories, although all were characterized by a preference for mechanistic types of explanation supported by great originality of technique and experiment. His studies of insects have a special quality all their own, while most of his other anatomical and physiological work may be called medical. The medical research was conducted within the fabric of currently fashionable theories, often actually in the company of his colleagues. This category includes his thesis on respiration, his book on the anatomy of the uterus, and other scattered notes. His accomplishments in this area were well known to his contemporaries but occasioned several priority disputes. By contrast, his work on insects was in a sense a private quest and remained largely unpublished during his lifetime. The theme of this work was essentially anti-Aristotelian, for he claimed that insects are no less perfect than higher animals and are not really different in their modes of development.

Swammerdam’s medical thesis offers a perfectly Cartesian mechanical explanation of the motion of the lungs and the function of breathing, supplemented by the iatrochemistry of Sylvius. Swammerdam struggled to avoid using any attractive powers, whether of the mouth, of the lungs themselves, or of a partial vacuum, to explain the rushing of air into the lungs. Apparently ignorant of Boyle’s idea that air has a springiness, Swammeredam argued that the muscular expansion of the chest outward pushes the ambient air down into the lungs. He dramatized this process with a submerged dog that could breathe through a tube. When the dog inhaled, the level of the water’s surface rose, but when the tube was stopped up, the lungs would not follow the chest in its expansion. The normal rising and falling of the lungs was simply the result of air having been pushed into them from outside, not of the motion of the thorax. (John Mayow, using Boyle’s ideas, easily destroyed Swammerdam’s argument in his tract on respiration in 1668.) Swammerdam described a very curious set of experiments, in which he produced bubbling by drawing air out of sealed containers partly filled with water; the experiments seem to be meant to show that the same effects producible by mouth suction can be duplicated with a syringe. Again, his point was that the action of breathing is mechanical.

swammerdam seems to have believed that when air in a confined space is pushed, the finer particles of air will run out of the container and the remaining air will then consist of heavier parts and will therefore be dense. This idea of the nature of air pressure allowed him to explain what happens in respiration thus: the expanded lungs press on the air contained in the pleural cavity, thus forcing the subtler parts out of this cavity into the heart. He had already demonstrated this process in January 1663, when his professors and fellow students saw him force air into the lungs of a living dog to produce a visible effervescence in the dog’s heart. While agreeing with Harvey that the heart does contract of its own power, Swammerdam integrated this with the Cartesian picture of the blood moving by virtue of its increase in volume as well, first in the right side before being cooled by the lungs, and then again when finally perfected on the left side, under the influence of the fine, subtle particles of air. Like Descartes, Swammerdam suggested that emotions like joy, anger, fear, and happiness depend upon the various degrees of motion of the blood in respiration.

Although so many of Swammerdam’s ideas about respiration appear misbegotten in the light of modern theory, or even in comparison to those of his contemporaries at Oxford, the assumptions and experimental technique behind them were essentially the same as those used in his classic proof that muscles do not increase in volume upon contraction. Again he was Cartesian in interpreting the old animal spirit, passing from nerves into muscle, as a very subtle but material fluid. Testing the reaction of various muscles of many different animals, Swammerdam learned that the frog was the best subject for this kind of experiment, and it was with this animal that he gave demonstrations to Steno about 1663 and to the Grand Prince Cosimo III in 1669.

The first part of Swammerdam’s demonstration was simply an elaboration of the common observation that a muscle can contract when separated from the body. Using both the heart and a long muscle of the frog separated from the body and the blood vessels, he urged that the fact that they would repeatedly respond to the stimulation of the nerve showed that contraction did not depend on an influx of matter from the brain or of blood, both current theories. Simply placing a muscle in a glass tube made the thickening of its belly and the shortening of its length clearly visible. The enlargement of the belly of a muscle had suggested to a number of men that contraction consists of effervescence or some other increase in volume, but Swammerdam devised an elegant experiment to measure the change in volume, but Swammerdom devised an elegant experiment to measure the change in volume, using his favorite instrument. Placing a muscle inside a syringe, the mouth of which was blocked by a drop of colored water, he was able to demonstrate that the contraction of the muscle or heart was not accompained by an outward motion of the drop; if there was motion at all, it was inward, suggesting a slight decrease in volume. Swammerdam did not suggest an alternate mechanism of contraction, nor did he deny the existence of a matter carried through the nerves, but simply noted that this matter must be of insensible volume. His description and drawings of this investigation were first published in 1738, but they were well known to Steno and through him to others, including Croone and Borelli.5

It was at Saumur that Swammerdam perfected a technique for displaying the valves of lymphatic vessels, although the existence of these valves was already known. Ruysch, who at Leiden had also been interested in techniques of anatomical preservation, published a description of a similar preparation in 1665. Swammerdam found that his father had shown his drawings to all who were interested, and although Ruysch was probably innocent, Swammerdam expressed annoyance.6

During his second stay at Leiden, in the winter of 1666–1667, Swammerdam and van Horne collaborated on the anatomy of human reproductive organs, both male and female. Swammerdam used wax injection to make the vessels distinct. Although van Horne described this anatomical work in 1668, Swammerdam did not publish his drawings of the preparations until de Graaf made public his own investigations on the same subject. Swammerdam then published Miraculum naturae, which he sent, along with the preserved specimens them selves (now lost), to the Royal Society asking that his priority be acknowledged. Besides the technique of wax injection, one of the discoveries in dispute was the very nature of human reproduction. According to van Horne, Steno, Swammerdam, and de Graaf, the organs that had been called female testes were really ovaries, like those of egglaying animals. Swammerdam claimed to have seen eggs in them. Baer in the nineteenth century is more properly credited with this observation, but the important concept that mammals do have ovaries was accepted in the seventeenth century. Although the Royal Society arbitrated the question of priority in favor of Steno, Harvey’s pronouncement that all life originates in eggs made their anatomical search a natural one.

In association with the Private College of Amsterdam, Swammerdam dissected the pancreas of fish and analyzed the pancreatic fluid in the context of Sylvius’ theory of digestion, and he also described the formation of hernias. The Private College decided to publish as a body, but Swammerdam later noted that certain of their discoveries were entirely his own. He had shown that the spinal marrow consisted of fibers that terminate in the brain and from which nerves proceed out.

Besides these medical studies, Swammerdam pursued a lifelong inquiry into the nature of lower animals. A visitor of 1662 noted that Swammerdam owned a colored copy of Mouffet’s entomology.7 He was actively collecting, observing, and dissecting insects in Saumur, in and around Paris, in Leiden, and to the end of his days in the countryside around Amsterdam. All he managed to publish was the Historia insectorum generalis, Part I, and a monograph on the mayfly, which, in the period of his religious crisis, became the occasion for an extended hymn to the Creator. But he left explicit instructions in his will for the publication of the rest of his entomological studies, and Boerhaave was probably accurately carrying out Swammerdam’s intentions when he integrated the text of the Historia (slightly revised) with the unpublished manuscripts, using it as a framework that further researches filled in.

Swammerdam’s thesis about insects was fundamentally new and significant. For his contemporaries, as for Aristotle, there existed three good arguments that not only placed the insects far from higher animals, but even tended to remove them from the realm of subjects open to scientific study. These arguments were: insects lack internal anatomy; they originate by spontaneous generation; and they develop by metamorphosis. Swammerdam believed that all three arguments were false and devoted a wide variety of investigations to refute these ideas.

The 1669 Historia was devoted to the over-throw of the idea of metamorphosis, as its title explains: “General Account of the Bloodless Animals, in Which Will be Clearly Set Forward the True Basis of Their Slow Growth of Limbs, the Vulgar Error of the Transformation, Also Called Metamorphosis, Will be Effectually Washed Away, and Comprehended Concisely in Four Distinct Orders of Changes, or Natural Budding Forth of Limbs.” The idea of metamorphosis, which Swammerdam was so determined to refute, was that of a sudden and total change from one kind of creature into another, comparable to the alchemical transmutation of a base metal into gold.

William Harvey, calling the starting point of life an egg, defined two distinct modes of development from an egg. The chick grows in a hen’s egg by epigenesis, but the butterfly grows in its “egg” (the chrysalis) by metamorphosis, as does an animal appearing in putrid matter. In epigenesis, the embryo is at first tiny and imperfect; it grows in size while acquiring its parts one after another. In metamorphosis the parts come into existence simultaneously and full-sized. Swammerdam consciously and energetically set out to destroy this supposed difference between the epigenetic development of higher animals and the metamorphic origin of lower animals. He used two kinds of evidence: the dissection of larvae and chrysalides before the final emergence of the adult, and a comparison among various types of insects including some that undergo only partial metamorphosis or none at all. It would seem that Swammerdam caught a clue to the nature of metamorphosis from his observations of the aquatic larvae of mayflies (which he first studied in 1661) and dragonflies (watched at Saumur in 1663 or 1664). The wings, which appear in so impressive a manner after the last molt, can be seen in a late larva, folded up in special protuberances on the back. The gradual growth of the insect can be easily seen in the successive larval stages. There is no difficulty in recognizing this process as the life cycle of one animal changing its form as it grows, just as the chick must change in appearance as well as in size before becoming a hen. Believing that the laws of nature are regular and simple, Swammerdam sought to explain all development according to one model. Those changes that seem metamorphic are really no different from the obviously gradual ones, except that they go on invisibly, under the skin.

Curious to find the growth of a butterfly’s wings to be as epigenetic as a dragonfly’s, Swammerdam searched for the proper dissecting technique. In his thesis of 1667 he had promised that he would soon explain the transformation of a caterpillar into a chrysalis, and by 1669 he had found that if a mature caterpillar, just preparing to become a chrysalis, is treated first with boiling water, then with wine and vinegar, and if the skin is removed, the rudiments of limbs and wings may be discerned. This demonstration was thought to be significant and exciting, both by Swammerdam and by his contemporaries, but there is no evidence for the dramatic scenes portrayed by Boerhaave, Francis J. Cole, and others. An eyewitness account undermines the picture of Swammerdam as a silent auditor at Thévenot’s gatherings.8 The most dramatic moment for Swammerdam himself may have been when he learned that Malpighi had anticipated him, finding rudiments of wings and legs in a silkworm.9 Swammerdam claimed to have done his dissection in the presence of Magalotti. which would have been in June or July 1669.10 Swammerdam regarded this demonstration as a great achievement, for the parts of the butterfly are so soft, tender, and folded that they can be recognized in a late caterpillar on the verge of its change only with difficulty. In a slightly younger caterpillar that is active and feeding they can scarcely be distinguished, because they are even more fluid and confused with the other tissue, he said. Swammerdam did not claim to have detected them in an immature caterpillar. They are at first invisible, in his description, not because of any extreme minuteness but because they are too fluid.

The point that Swammerdam considered most important, since it destroyed the previous ideas of metamorphosis, is that the parts of the butterfly do not come into being suddenly in the chrysalis but are already beginning to grow in the caterpillar. They develop by epigenesis, the process that Harvey described for higher animals, not by metamorphosis:

[The limbs] which a worm without legs acquires near the chest after its change are not born in the suddenness of changing, or, to speak more exactly, in the quickness of a budding out or rising up of limbs, but these are growing with the worm at their designated places under the skin, one after another by addition, that is, by epigenesis11 and these parts are not born suddenly, but grow on slowly, the one part after the other … and they are increased and born in this swelling, budding forth, rising up, budding, and as if stretching of new limbs, gradually by an addition of parts, epigenesis, and by no means by a transformation, metamorphosis; therein lies the sole foundation of all the changes of bloodless animals.12

Swammerdam’s principal concern was with development, not origin. After 1669 he studied the process of development in the chrysalis in more detail. He dissected chrysalides after two days, six days, twelve days, and sixteen days, reporting that structures at first so fluid and delicate that they cannot be handled gradually acquire form and firmness.

The sole foundation of all the so-called transformations of insects, according to Swammerdam, is the Popken or Nympha, that is, a pupa. His definition of this new concept is unclear, but he was fairly consistent in using it for the stage where an insect is preparing to molt by growing a new inner skin. Swammerdam’s explanation of the nature of the pupa put great emphasis on the idea that the individual animal always remains the same, that is, we are dealing with the life history of one individual, irrespective of moltings and changes in appearance:

... a nymph, pupa, or chrysalis is nothing other than such a manner of change from a worm and caterpillar, or, to speak more exactly, such a manner of growing, swelling, budding, or protuberance of parts of a worm or caterpillar, as to bear the specific shape of the future animal itself; or, otherwise, that this growth and so forth of parts in a worm or caterpillar is the animal itself in the form of a pupa. So that the matter being properly considered, a worm or caterpillar does not change into a pupa, but becomes a pupa by the growing of parts; so also this pupa, we may add, afterward does not change into a flying beast, but the same worm or caterpillar, having taken on the form of a pupa by shedding its skin, becomes a flying beast. The above changes are nothing else than those of a chick, which is not changed into a hen, but becomes a hen by the growing of its parts: or also, of the young of a frog which does not change into a frog, but becomes a frog by the swelling of its parts.13

After describing the mistaken notion of metamorphosis to be found in Thomas Mouffet, Goedaert, and Harvey, and indicating the pupa as the true basis of all insect development, Swammerdam proposed that all the various modes of insect development fall into one of four groups. The first group comprehends those insects that hatch from the egg in their adult form, afterward undergoing no change save growth. Before hatching, the animal lies inside the eggshell motionless, without food, and occupying the entire volume of the egg. Swammerdam regarded the egg itself as really a kind of pupa. “The animal grew within its mother from invisible but nevertheless real beginnings.”14 The animal’s first development having taken place within the parent, what looks like an egg in this class is a formed animal lying hidden under a skin, that is, a pupa. In Swammerdam’s view, this mode of development is the most obvious and simple to understand.

In the remaining three orders of development, the animal hatches out of its egg before having reached perfection, so it must become a pupa before appearing in its final shape. In the second kind of development, the animal emerges from its egg without wings, but usually with six legs. It acquires its adult structures by a gradual and visible external process of growth. In some members of the group, such as the earwigs, the difference between the young “worm” and the adult are very slight, consisting only in the addition of wings. In others, such as the mayfly, the changes are greater, involving the loss of larval structures as well as the addition of the adult structures. In all cases the adult structures are acquired by visible external growth, and the animal never completely loses its ability to move. The pupa in this second order is simply the last stage before the final molt from which the winged adult emerges.

Swammerdam understood all remaining modes of development to be fundamentally the same, and to differ from the first two groups in the same respect. He defined them in two more groups, while pointing out that the fourth could justifiably have been included within the third. In both these orders the animal leaves its egg in as yet a very imperfect state, lacking many or most of its adult structures. These it acquires in the course of time, gradually, invisibly, under the skin, where the structures lie folded and soft. The adult parts are all existent and recognizable in the pupa, although in some insects they are very obscure. The pupa in both orders does not feed or move.

Swammerdam divided his third order of development into two subgroups, those whose adult parts are obvious in the pupa because of its thin skin and those whose pupa seems to be without parts externally. The nymphs of ants, bees, and beetles are pupae of the first kind, and the chrysalides or aureliae of butterflies and moths are pupae of the second kind. He believed the difference between them to be merely a matter of the thickness of their skin, and even tried to find a simple mechanical explanation for this difference.

Swammerdam’s fourth order of insect development is comprised of insects whose pupa, corresponding exactly to the nympth or chrysalis of the third order, is hidden. This is what happens in most flies; their larvae or maggots from a case called a puparium. Swammerdam insisted that the difference between the third and fourth order is one of appearance only, not of essence. The pupa separates from the larval skin, as in the second and third orders, but the animal does not crawl out of this skin, which hardens to form the puparium. The pupa lies within this case just as the bee’s pupa lies sealed in its wax cell. The puparium may retain the shape of the larva, that is, be worm-shaped, or it may round up into the shape of an egg. It is of great importance to recognize, wrote Swammerdam, that it worm-or egg-shaped object is not an egg, as Harvey and others had said, nor a kind of pupa, but that it contains a pupa. Yet Swammerdam himself did see all eggs as pupae in one sense, insofar as they contained and concealed an animal.

Swammerdam emphasized the theme and structure of his insect research by appending to the Historia a table designed to show that insects develop in essentially the same fashion as do all other living things. All begin in an egg, grow gradually in size and detail until arriving at adulthood, when they are sexually mature. Swammerdam used the frog to illustrate development in higher animals and the carnation to illustrate development in plants. His table presents insects from each of his orders of development, the louse for the first order, the dragonfly for the second, the ant and the moth for the nymph and chrysalis types of the third order, and the dung fly for the fourth order. Five stages of development from egg to adult are numbered, and the numbers correspond to the figures in his tables, which had evidently been carefully planned with this comparison in mind.

Of the three arguments for the imperfection of insects, Swammerdam’s Historia was concerned with the refutation of only one, metamorphosis as then understood. Working after 1669, Swammerdam attacked the other two arguments as well. In spite of his famous experiments on maggots in meat, Redi decided that insects found inside plants must have appeared there without parents; the Latin edition of Redi’s work, appearing in Amsterdam in 1671, stimulated Swammerdam to collect information about insects that cause plant galls. The idea that insects consisted internally of humors was destroyed by Swammerdam’s exceptional skills at microdissection; he refined his technique of injecting fluids, including wax, mercury, air, and alcohol; and he often used very fine scissors instead of knives15 He used a single-lens microscope made by Jan Hudde of Amsterdam,16 and another mounted on flexible arms made by Samuel Musschenbroek17.

It is not surprising to find such a skilled microscopist as Swammerdam reporting that a frog embryo consists of globules or that there are oval particles in the blood, but historians should note that he attempted no interpretation of these observations. His dissections of various insects, as well as snails, mussels, cuttlefish, a Portuguese man-of-war, and a hermit crab formed a good portion of the study of all invertebrate anatomy before Cuvier.

Swammerdam’s four orders of insect development were transformed by John Ray and Martin Lister into four orders of insects.18 In the subsequent history of classification, types of development played various roles (Linnaeus did not use them), but clearly Swammerdam’s own purpose had not been taxonomic.

Swammerdam is commonly called the founder of the theory of preformation. This is ironic because, Swammerdam, like Malpighi, consciously avoided conjecture. The reciprocal intercourse of snails, pictured in his medical thesis, was in a sense the emblem of all his science, for it represented to him the fact that even the safe assumption that animals are either male or female can be destroyed by an observation. He was loath to let his reasoning run beyond his facts. Still, Swammerdam’s work did contribute to the development of the idea of preexistence and even emboîtement. His opposition to sudden metamorphosis could easily be read as an opposition to any change at all, for his own concept of the pupa was obscure, and he had no clear notion of the distinction between growth and differentiation.

Swammerdam opposed both spontaneous generation and metamorphosis on the grounds that they led to atheism by allowing chance and accident to rule instead of law and regularity. The basic law of living things was that they came from parents of the same kind by means of eggs. Nor is their growth in the egg subject to chance, as pangenesis, for example, might suggest, but is simply the increase of parts already present. The actual nature of the egg itself was a very difficult question that Swammerdam realized he had no means of solving. But if growth is conceivable while change in substance is not, inevitably the germs of all living things must have been in existence from the time of Creation. Swammerdam alluded to this idea only briefly. It was probable, said Swammerdam in 1669, that there was no generation of the sort that could leave room for chance processes, but only propagation, that is, the growth of something already in existence.19 Certainly Swammerdam had no full emboîtement theory clearly in mind, for he located the first principles in the egg produced by the female ovary, yet suggested that this concept might explain the biblical statement that Levi was in his father’s loins (Hebrews 7:10). He identified the black spot of a frog’s egg as itself a frog with all its parts, without claiming to have seen a miniature, but on the contrary expressing wonder that somehow a tiny black spot really is a frog.20

Swammerdam said that he communicated his experiments to a learned man, who suggested that they could even explain how Adam’s sin affected all his descendants,21 and that when Eve’s eggs were used up the human race would end,22 but on all such questions Swammerdam forbore to give an opinion himself. It has always been assumed that it was Malebranche to whom Swammerdam referred. Certainly Malebranche was very quick to incorporate Swammerdam’s information into his own philosophy.23 The manuscripts Swammerdam left in 1680 contain no elaboration of the preformationist paragraphs of 1669 and 1672, but did include a careful description of the complete transformations of anatomy to be seen when a beetle larva becomes an adult, the mere watery humor that is visible in bee eggs, and the beginning of a frog in four globules.

Some biographers describe Swammerdam as a mystic, for he was a follower of a woman who purportedly had spoken with God, and he saw in the short flight of the mayfly an image of man’s own brief existence. Yet the word mystical certainly does not apply to his scientific work, for his was a mechanistic world, instituted by God and operating like clockwork.


1. See Engel, “Records,” cited in the bibliography.

2.Book of Nature, 117.

3. Antoni van Leeuwenhoek, The Collected Letters, I (Amsterdam, 1939), 143, letter to Oldenburg of 7 September 1674.

4. Howard B. Adelmann, Marcello Malpighi and the Evolution of Embryology, 1 (Ithaca, 1966), 399.

5. Leonard G. Wilson, “William Croone’s Theory of Muscular Contraction,” in Notes and Records. Royal Society of London, 16 (1961), 158–178.

6. A. M. Luyendijk-Elshout, Introduction to Frederik Ruysch. Dilucidatio Valvularum in Vasis et Lacteis (1665), facsimile (1964).

7. Johan Nordström, “Swammerdamiana: Excerpts From the Travel Journal of Olaus Borrichius and Two Letters from Swammerdam to Thévenot.” in Lychnos (1954–1955), 21–65.


9. Swammerdam, Historia, 131: Book of Nature, II, 2. Adelmann, Malpighi, II, 844–845.

10. Anxious to establish his priority over Malpighi, whose Debombyce appeared in 1669 (see Adelmann, I, 399), Swammerdam would undoubtedly have mentioned any public demonstration of years before. Instead he refers to a visit from Thévenot and Magalotti. which would have been during the tour of the Grand Prince (not yet Duke) of Tuscany, Cosimo III. (He does not claim that the Prince himself witnessed this dissection, though he mentions showing him other discoveries). Careful records of the curiosities seen on the tour of 1667–1668 and references to Thévenot on the summer tour of 1669 are the basis for my dating of the visit with Swammerdam. See G. J. Hoogewerff. De Twee Reizen van Cosimo de’ Medici Prins van Toscane door de Nederlanden (1667–1669): Journalen en Documenten (Amsterdam, 1919), xlix, 45, 319, 392.

11. My literal translation of the Dutch Historia, 26.

12.Ibid., 43.

13.Ibid., 8–9. My interpretation differs from those based on the Flloyd translation, The Book of Nature.

14.Ibid., p. 100.

15. Boerhaave, Book of Nature. xiv–xvi.

16. Swammerdam, Historia, 81. See also Balthasar de Monconys, Journal des Voyages, II (Lyons, 1665–1666), 161–162.

17. Boerhaave, loc cit.

18. John Ray, Historia Insectorum (London, 1710).

19. Swammerdam, Historia, 51.

20. Swammerdam, Miraculum, 21.

21.Historia, 52.

22. Swammerdam, Miraculum, 22.

23. Paul Schrecker, “Malebranche et le préformisme biologique,” in Revue internationale de philosophie, 1 (1938), 77–97.


I. Original Works. All of Swammerdam’s works appeared in various printings and translations. A complete bibliography. including some other authors who cited him, is given in Schierbeek’s biography.

Swammerdam’s works include Tractatus physico-an-atomico-medicus de respiratione usuque pulmonum (Leiden, 1667), reprinted, with Dutch trans., in Opuscula selecta de arte medica neerlandicorum, VI (Amsterdam, 1927), 46–181; Historia insectorum generalis, ofte, Algemeene Verhandeling van de Bloedeloose Dierkens ... (Utrecht, 1669), French trans., 1682, repr., 1685, and Latin trans., 1685, repr., 1693. Its text is incorporated into the Biblia Naturae.

Other works are Miraculum naturae sive uteri muliebris fabrica (Leiden, 1672), repr., 1679, 1680, 1717 (and 1729?); Ephemeri vita of afbeeldingh van’s Menschen Leven, vertoont in de Wonderbaarelijcke en nooyt gehoorde Historie van het vliegent ende een-dagh-levent Haft of Oever-aas (Amsterdam, 1675), of which the biological portions, without the hymns to the Creator, were published in English by Edward Tyson as Ephemeri vita (London, 1681), and in French in Thévenot’s Recueil des voyages: Bybel der Natuure (Leiden, 1737–1738), with facing pages in Latin, Biblia naturae, sive historia inśectorum, 3 vols.; German trans. (Leipzig, 1752); in English as The Book of Nature, Thomas Flloyd, trans., with footnotes by John Hill (London, 1758).

II. Secondary Literature. In 1727 Boerhaave purchased Swammerdam’s manuscripts; he also acquired some papers of biographical interest, including forty-one of Swammerdam’s letters to Thévenot. These manuscripts and papers are now in the Universitäts-bibliothek in Göttingen, and a microfilm of them is in Leiden. To this day Boerhaave remains the only scholar to have made use of these papers, so his biography, prefacing the Biblia naturae in all its editions, is the chief source for Swammerdam’s life. In spite of the fact that parts of it are evidently conjecture, it is on the whole useful and reliable.

Abraham Schierbeek in 1944 combined Boerhaave’s biography with later sources and Swammerdam’s text when writing his Jan Swammerdam, zijn Leven en zijn Werken (N.V. Uitgeversmaatschappij “De Tijdstroom” Lochem [1947]); Jan Swammerdam (12 February 1637–17 February 1680): His Life and Works (Amsterdam, 1967).

Sources of information not in Boerhaave, or valuable interpretations, are the following: Francis J. Cole, “The Birthplace of Jan Swammerdam, 1637–1680,” in Isis, 27 (1937), 452; Hendrik Engel, “Records on Jan Swammerdam in the Amsterdam Archives,” in Centaurus, 1 (1950), 143–155; and Observationes anatomicae selectores collegii privat: Amstelodamensi um 1667–1673, F. J. Cole, ed. (Reading, England, 1938).

On preformation, preexistence, and emboîtement, see Jacques Roger, Les sciences de la vie dans la pensée francaise du XVIIIe siècle (1963), especially pp. 325–384; Howard B. Adelmann, Marcello Malpighi and the Evolution of Embryology (Ithaca, N.Y., 1966), 819–886; and Peter J. Bowler, “Preformation and Pre-existence in the Seventeenth Century: A Brief Analysis,” in Journal of the History of Biology, 4 (1971), 221–244.

Mary P. Winsor

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Jan Swammerdam

Jan Swammerdam

The Dutch natural scientist Jan Swammerdam (1637-1680) was a founder of comparative anatomy and entomology and was very skillful in the art of microdissection.

Jan Swammerdam was born on Feb. 12, 1637, in Amsterdam. His father, a prosperous apothecary, had collected a museum of curiosities. Jan soon developed a passion for natural history, in particular for the study of insects. His collection of insects, begun in his youth, eventually included some 3, 000 species. At the age of 24 he went to Leiden to study medicine, where he graduated in 1667. His graduation thesis included the observation that the lung of a newborn mammal sinks in water but floats once the animal has breathed. Much to his father's displeasure, Swammerdam did not practice medicine but continued his microdissections of insects.

Swammerdam designed a simple dissecting microscope that had two arms: one for holding the object and the other for the lens; the arms had coarse and fine adjustments. He used very fine scissors for dissection and capillary tubes of glass for inflating or injecting blood vessels. He was one of the first to dissect under water and to remove fat by organic solvents. In 1669 he published his "General account of bloodless animalculae, " a history of insects which dealt with their modes of transformation and development.

His interest in religion led Swammerdam to meet the Flemish mystic Antoinette Bourignon in 1673, who had a profound influence on his life. At this time he was engaged in a study of the life history of the mayfly which was, to Antoinette Bourignon, a "little beast which lives for only a single day, and throughout that time endures many miseries." She reluctantly allowed Swammerdam to publish his studies in 1675 (Emphemerae vita) on condition that he would study religion in the future. The book contains many remarkable pieces of minute anatomy, but these were diluted by allusions to the Bible and the development of an ethical system. During the remainder of his life he sufferred from periods of depression, during which he destroyed much of his work. He died on Feb. 17, 1680.

Swammerdam left many manuscripts which Hermann Boerhaave published in 1737 in two volumes called Biblia naturae (Bible of Nature). This book, which contained work done mainly between 1668 and 1675, is the finest collection of microscopical observations ever produced by one worker, and some of the figures have never been excelled. The book is the foundation of our modern knowledge of the structure, metamorphosis, and classification of insects. It also includes detailed observations on the Crustacea and Mollusca and on the life history of the frog.

Perhaps the most complete study is that on the honeybee, which is illustrated by beautiful drawings. In his studies on the frog, Swammerdam used a nerve-muscle preparation and invented a form of plethysmograph. He established that when the nerve was mechanically stimulated the muscle contracted, and he contradicted the idea, accepted in his time, that when a muscle contracted it increased in volume due to the passage of liquid from nerve to muscle.

Further Reading

Abraham Schierbeek, Jan Swammerdam (trans. 1967), is the only modern biography. For Swammerdam's place in the history of biology, the student can consult Charles Singer, A History of Biology to about the Year 1900 (1931; 3d ed. 1959); F. J. Cole, A History of Comparative Anatomy from Aristotle to the Eighteenth Century (1944); and M. J. Sirks and Conway Zirkle, The Evolution of Biology (1964). □

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Swammerdam, Jan

Jan Swammerdam (yän vä´mərdäm), 1637–80, Dutch naturalist. He was a pioneer in the use of the microscope. Before he turned to religious contemplation his chief interest was the study of invertebrates. He investigated the life histories of frogs and of numerous insects, which he classified on the basis of their metamorphic development. He also made valuable observations on human anatomy and was probably the first to detect red blood cells (1658). A composite collection of his descriptions and of his accurate and exquisitely executed drawings was published posthumously (2 vol., 1737–38) and appeared in English as The Book of Nature (1758). He was an early and influential proponent of the theory of evolution, in opposition to the current belief in spontaneous generation.

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