By Eric Jorink
On 4 March 1673, Johannes Swammerdam sent a letter to Henry Oldenburg, including these images (fig. 1). Only an abstract of the letter appeared in the Philosophical Transactions (19 May 1673, page 6041), without including what was basically the point of the message: a visual report of observations of the pulmonary arteries of a frog, and of the genital system of the horn-noosed beetle. As a biographer of Swammerdam, I find these images fascinating, both for their intrinsic quality, as for the fact that they are a nice point of departure for some thoughts on the role of the visual in early modern scientific culture.
Like Robert Hooke, Swammerdam was a skilled draftsman. During his years as a student in Leiden (1661-1667) he did pioneering research on insects, toads and other forms of low life. Swammerdam maintained that all creatures, great and small, obeyed the same laws of nature. He rejected the theory of spontaneous generation, according to which insects were devoid of an internal anatomy and had their origin in decaying flesh or plants.
Swammerdam considered it his duty to point to the marvels of God’s creation. Swammerdam was very much aware of his talent as an anatomist and draftsman. He applauded the publication of Hooke’s Micrographia (1665), Redi’s Esperienze intorno alla generazione degl’insetti (1668) and Malpighi’s De Bombyce (published by the Royal Society in 1669) and considered them as allies in his campaign against spontaneous generation.
In his Historia insectorum generalis (1669) Swammerdam demonstrated that all insects come from eggs, and all go through a stage-like development. Occasionally, he also went into a visual dialogue with Hooke (figs 2 and 3). Whereas the latter famously had represented the alien micro-world with no visual clues of the absolute size and context of the objects portrayed, Swammerdam employed a technique in which each creature was represented both life-size, and magnified. The microscope was only used occasionally. Graphically, he showed the uniformity of nature, pointing at similarities between the development of an insect, frog and carnation (figs 4 and 5).
In Historia insectorum Swammerdam concentrated on the outward appearance of insects. Inspired by the work of Malpighi from 1670 he now focused on anatomizing and using the microscope more intensively. Studying and representing the inner parts of these tiny creatures required new visual techniques. Since Swammerdam observed what no one before him had seen, he had to train his eye with regard to the observations, and invent ways to represent them. Without external aid, showing the strange and previously unseen forms of isolated organs of a creature would make no sense.
The images Swammerdam sent to Oldenburg could be seen as experiments in form. Compared to the visual strategy he previously used, Swammerdam was now both zooming in and zooming out. To make an easy start: the creature depicted in figure V in the right lower corner marked A (see fig. 1 above) is easily recognizable as a nose-horned beetle (depicted at life size). The drawing is deceptively simple, but shows Swammerdam’s talent to represent the creature with just a few well-chosen lines and brushes of ink. Swammerdam deeply admired the work of artist Joris Hoefnagel (1542-1600), who at the end of the sixteenth century had made pioneering watercolors of all kinds of insects. We could read Swammerdam’s sketch as a self-aware introduction to the beholder – see how easily I can draw things familiar to you; you can also trust me when I show you places and things unknown to you. Later drawings by Swammerdam of the nose-horned beetle (fig. 5) are much more elaborated, and can be seen as explicit references not only to Hoefnagel but also to the works of art by Jacques de Gheyn (1565-1629) and even Albrecht Dürer.
By now, we should refer to the letter. By focusing on the creature’s inner parts, Swammerdam uses the strategy of both mapmakers and earlier anatomists: the legend. He writes: ‘Figure V expresses to the life (‘ad vivum exprimit’) the genitalia of the horn-nosed beetle. A the beetle, B the horny part of the penis, C the place from which the penis protrudes when erect….’ Etcetera. What we see are interior details: strangely shaped organs, curled lines, flower-shaped structures. Using a legend is a successful strategy here, and perhaps the only workable way in representing the previously unknown. Moreover, as Swammerdam occasionally stressed to his readers, the slightly stylized drawings also helped the observer who for the first time would enter this unknown territory to discern and identify the organs in there. Swammerdam also employs this strategy in the Figures I-IV (fig. 1), where he illustrates the passage in which he explains in painstaking detail the pulmonary artery system of the frog. These drawings are the few by Swammerdam I know of in which color is used. This had a practical reason: the drawings represent, as Swammerdam put it, ‘graphically’ (‘graphice exprimit’) how the structure within the lungs had been made visible by injecting colored wax. Hence, what we see is a representation of a preparation interacting with a text.
The point is, of course, that without the accompanying letter, the images become meaningless, and vice versa. Some of Swammerdam’s letters and images are still at the archives of the Royal Society (now separated, to be sure). They remind us that in the scientific culture of the 1670s the boundaries between words and images, and between science and art, were still rather fluent ones.