Trained as a doctor in the prestigious new university of Leiden, Swammerdam was one of a group of highly talented students that included de Graaf (1641-1673), Stenson (1638-1686) and Ruysch (1638-1728), each of whom made a major contribution to science.
Among his many anatomical and medical discoveries, Swammerdam found that muscles do not expand when contracted, that eggs are present in the human ovary, that there are valves in the lymphatic vessels and that penile erection is due to an influx of blood.
He also carried out a series of brilliant physiological studies of respiration, pioneered the frog nerve-muscle preparation, made pioneering dissections of the female genital tract, was one of the first to observe red blood cells, developed a novel method for preserving anatomical specimens involving the injection of hot wax, described the anatomy of the uterus and discovered the nature of hernias.
Even if this was the sum total of his lifes work, Swammerdam would clearly merit a place in the history of anatomy and medicine. However, in the 1670s, his work went far beyond these rather unfocused findings and took biology as a whole onto a new plane.
Swammerdams work on insects
From childhood, Swammerdam was passionately interested in insects, to the continued annoyance of his father, an apothecary who hoped that Jan would practice medicine (he never did) and earn himself a living (ditto).
In the late 1660s, Swammerdam began to dissect insects he was the first to realise that the king bee was in fact a queen, when he discovered her ovaries. It was in 1669 that Swammerdam realised he could combine his anatomical skills and the microscope. His friend and patron, the French diplomat and man of letters Melchisedec Thévenot (1620?-1692), sent him a copy of Malpighis recently-published monograph De Bombyce (1669), a pioneering account of the micro-dissection of the silk-worm larva.
This magnificent work clearly inspired Swammerdam, and throughout the 1670s, despite repeated attacks of malaria and a brief interlude during which he abandoned his scientific work for religious contemplation, he made a series of dissections of insects, demonstrating that they contained complex internal organs, thus breaking with two millennia of Aristotelian tradition. His massive work on bees and insects was renowned even before publication.
These studies were finally summarised in his magisterial Bible of Nature, published posthumously in 1737-8 by the great Dutch physician, Herman Boerhaave.
Swammerdam and development
Despite the many discoveries he made in insect anatomy and natural history, Swammerdams most important and most misunderstood contribution was to the study of development.
He asserted two fundamental truths: first, that there is no such thing as spontaneous generation, and second that the various stages in the insects life-cycle egg, larva, pupa and adult merely represent different forms of the same individual.
At the time, these two positions were closely linked; thus Swammerdam argued in The Bible of Nature that his work eradicates entirely the false notion of metamorphosis or change of one creature into another, that universal chimera of erring opinions, and totally destroys and subverts the monstrous opinion of a fortuitous generation of creatures.
From his 1669 work Historia Insectorum Generalis onwards, Swammerdam sought to integrate his observations into a general classification of insects by discovering the rules and theorems of morphogenesis an ambitious project, even today.
He identified four orders of insects (the definition of the time was much looser than todays) corresponding to different developmental pathways.
The first, and simplest, is a diverse groups of creatures such as spiders, scorpions, snails and ametabolous insects (such as lice) where the adult form hatches directly out of the egg.
In the second order (which includes dragonflies, locusts and the may-fly), a nymph hatches out of the egg and then gradually develops into the adult form.
The third and fourth orders holometabolous insects with a pupal stage, such as butterflies, bees or flies are those that posed the greatest intellectual challenge at the time, and remain poorly understood today.
For a discussion of some implications of these findings for the development of the theory of preformationism click here.
Swammerdam was perpetually plagued by financial problems and found himself in permanent conflict first with his father, then with his sister. In his personal life he swung between bouts of mystical intensity and a near-religious devotion to his scientific observations, with only a few close friends, such as Matthew Slade or Thévenot providing him with continual support and encouragement.
However, as his unending joy faced with the natural world makes clear, he was not a dour man. The care with which he reared a wide variety of insects in his room (and indeed on his body!), carefully noting their habits and duration of development under different conditions shows that his delicate and precise methodology was not restricted to dissection.
His view of insect behaviour and development, while lawful, was not mechanical or Cartesian. His delightfully anthropomorphic description of post-coital fatigue in the snail speaks volumes in terms of his attempt to understand animal behaviour and his conception of the factors that motivate animals:
"After all is finished, the little creature, having wantonly consumed the strength of life, becomes dull and heavy; and thence calmly retiring into its shell, rests quietly without much creeping, until the furious lust of generation gathers new strength, and effaces the memory of the uneasiness suffered after the former coition."
Of all the natural historians of the 17th century, Swammerdam probably contributed most to the key debates of the time, by demonstrating that insects were just as complex as larger creatures, and by showing that no example of spontaneous generation could resist investigation.
In this respect, he even surpassed Redi (1626-1697), a fierce opponent of spontaneous generation in general, but who accepted that gall-insects were produced by putrefaction. Swammerdams careful dissections and observation proved Redi wrong and showed that they hatched from eggs laid by adults:
This led Swammerdam to state the following aphorism: "All animals hatch from eggs that are laid by a female of the same species". Swammerdam thus showed that all animals including insects bred true. The "fixity" of species was a prerequisite for the subsequent recognition of evolution.
In the 18th century, Swammerdams work became widely known following the publication of The Book of Nature. Less than six years after it appeared, Reaumur, one of the greatest scientists of the century, reproduced Swammerdams dissection of bee ovaries in his book on bees, praising its quality.
And Lyonet, whose work on insect anatomy built upon that of Swammerdam, said of his predecessors work that it surpasses the imagination and savours of the prodigious. Indeed. Whatever his mistakes, whatever the contradictions between his science and his mystical theology, Swammerdam made a massive contribution to the history of biology.
This page is partly excerpted and adapted from an article that appeared in Endeavour (2000) 24(3) pp122-128. ©Elsevier Science, 2000.
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