Suddenly our large video screen was crawling with fidgeting tadpoles. It was March 2022 and during the third round of MicroLabs we, the Visualizing the Unknown team looked, at human fluids: breast milk, blood and semen. Three anonymous persons had donated semen, and we were studying it’s appearance through old lenses, projected on a modern screen.
How difficult would it be to get a good picture of the life in that sperm? Seventeenth century microscopists Antoni van Leeuwenhoek hadn’t succeeded at first: ‘I remember that some three or four years ago I examined seminal fluid […] and that I then considered those animalcules to be globules’, he wrote in November of 1677. But in the end he saw he a multitude of ‘little animals’ which he compared to a small earth-nuts.
We had some initial difficulties too, but after trying for a while, we saw the small earth-nuts move. However, we didn’t fully succeed at recreating Van Leeuwenhoek’s experience. According to him, semen largely consisted of ‘all manner of great and small vessels, so various and so numerous that I have not the least doubt that they are nerves, arteries and veins’. We know those vessels don’t exist but would observations through Van Leeuwenhoek’s lenses give a hint as to why he thought they were there? No, we concluded.
And why did Van Leeuwenhoek decide that ‘blood-globules’ existed of six smaller globules? While studying blood through his lenses, we didn’t see any answers to that question.
Luckily, the observations of bodily fluids did yield a lot of experiential knowledge. About the advantages of glass capillaries, for example, which make body fluids easy to handle and, thanks to their shape, help to visualize microlife in various ways.