Valentine's Day Science: Replacing Romance with Discovery

I am reading Generation: The Seventeenth-Century Scientists Who Unraveled the Secrets of Sex, Life, and Growth, and came across a humorous passage last night.

Anton van Leeuwenhoek (lay-wen-hook) was a seventeenth-century Dutchman, who is remembered as the 'father of microbiology' for his improvement of the microscope and resulting discovery of microorganisms. He eventually turned his interest toward bodily fluids, including semen. Using his own, he was the first to observe spermatozoa.

As he later reassured the Royal Society, this semen 'was not obtained by any sinful contrivance on my part', but was 'the excess which Nature provided me in my conjugal relations.' What this means is that a few seconds before making one of the most surprising discoveries in the history of science, Leeuwenhoek had been making love to his wife, Cornelia....Corelia's opinion is not recorded. (pg. 202)