Visited by Johannes Swammerdam

August 15, 1674

Visited twice by Johannes Swammerdam (1637-1680) in late August.

The "gentleman" accompanying him could have been Arent Seijen, whom Constantijn Huygens linked with Swammerdam the previous February and who also visited Leeuwenhoek earlier in August 1674. It is more likely that the gentleman was Johan Ortt, whom Swammerdam writes about in Bijbel der Natuur.

As a young boy, Johan Ortt (1642-1701) lost his father, a wealthy cloth merchant in Amsterdam. As a young man, Ortt travelled around Europe. In Paris he met Christiaan Huygens and Thevenot. In Amsterdam, he became friends with Swammerdam. Together, they went to the zoo of the Palace at Hondelersdijk and walked from the Hague to Scheveningen. They also went to Delft to visit Leeuwenhoek. A week after that Swammerdam again visited Leeuwenhoek. He wanted to see the red blood cells through a good Leeuwenhoek microscope. Leeuwenhoek was annoyed, and expressed that in a letter to Oldenburg.


Letter 6 (AB 11) of September 7, 1674 to Henry Oldenburg

Dr. Swammerdam hath again within this fortnight visited me twice, accompanied with a Gentleman, to both which I have shew'd many of these Microscopical Observations, and of such others as I had formerly spoken to him about; perceiving that his speculations are busy upon this subject, and that probably he will discourse more largely of it than I have done hitherto. Though I liberally communicate my observations, I daily experience more and more that some are altogether incommunicative as regards their considerations, nay, do not scruple to point out my mistakes.