Govert Bidloo wrote Letter L-338 to Leeuwenhoek about little animals in sheep's livers

March 21, 1698

No manuscript is known.

This letter was published in 1698 by Henrik van Kroonevelt (who lived next door to Leeuwenhoek) with the title

Brief van G. Bidloo aan Antony van Leeuwenhoek: Wegens de dieren, welke men zomtyds in de lever der Schaapen en andere beestern vind

Letter of G. Bidloo to Antony van Leeuwenhoek: About the animals which are sometimes found in the liver of Sheep and other beasts

Kroonevelt also printed many of his letters, including Sevende Vervolg der Brieven, the 1702 edition, copies of which often have Bidloo’s letter bound after the index. It was summarized and reviewed anonymously in Philosophical Transactions, vol. 22, no. 263 (April 1700), p. 571 (should be p. 579).

In 1694, Govert Bidloo (1649-1713) was appointed professor of anatomy and medicine at Leiden University, succeeding Anton Nuck. Two years later, he was elected a fellow of the Royal Society, and in 1701 he became the personal physician of William III, the Dutch stadholder and king of England, Scotland and Ireland. In 1686, Bidloo wrote the libretto for the first-ever Dutch opera, Johan Schenck’s Ceres, Venus en Bacchus. He was succeeded at the university by Hermann Boerhaave.

In this letter, Bidloo presents a thorough study of the worms found in a sheep’s liver and its nearby parts. He describes the worms’ bodies, where they are found, their numbers and propagation, and how they cause diseases. He lists many of the authors who have found worms in various animals, including humans, and in which parts of their bodies the worms were found. He argues against the practices of quacks and many physicians who do not reason from evidence and mistake the symptoms of diseases for their causes.

As an extended discussion focused on one topic with copious references to prior literature, Bidloo's letter is an example of what is now known as a scientific article, in sharp contrast to a typical letter from Leeuwenhoek, which almost always includes multiple, often unrelated, topics and rarely a discussion of prior literature.

Fourteen figures illustrate this letter. The original drawings have been lost. In Krooneveld’s editions, figures 1–3 are inserted on p. 4, an unlabeled figure is inserted on p. 5, figure E is on p. 6, and the remaining figures face p. 7.

In this letter, Bidloo mentions some letters that have not survived and are not otherwise known. In addition to the lost Letter L-334 of 19 January 1698, only one letter that Leeuwenhoek wrote to Bidloo is known, Letter L-444 of 7 March 1706, along with Bidloo’s reply, Letter L-445 of 12 March 1706. Both of those are also lost but Leeuwenhoek quoted from Letter L-444 at length in Letter L-447 of 20 April 1706 to the Royal Society.


Med Hist. 1974 Apr; 18(2): 203–204

When an English translation of the letter by J. Jansen was published (Nieuwkoop: De Graaf) in 1972, an anonymous reviewer for the journal Medical History wrote:

Govert Bidloo (1649-1713), anatomist and surgeon, had made microscopic observations on certain animalcules and ova found in the bile passages, and now identified as F. hepatica. He was not the first to note the parasites, for his study contains abundant references to the work of predecessors, but he made surprisingly accurate descriptions and references (along with many errors). He disclosed his findings and conclusions in a letter to Leeuwenhoek.

Bidloo describes and illustrates the morphology, and thus permits us to compare his findings with the more precise knowledge of modem biology. Bidloo made some erroneous statements and drew some erroneous conclusions, but error, when studied in its context, is perhaps the best way of tracing the progress of science. His speculations regarding the development of the parasite and the relationship of these and other worms to disease are extremely interesting and throw much light on basic concepts of seventeenth-century medicine. At the same time the text obliquely illuminates the personality of the author and the customs of the times, in regard to communications.