We can thank Dutch textile merchant Antonie van Leeuwenhoek (1623-1732) for being interested enough in lens-making to kick-start the novel discipline of microscopy. Leeuwenhoek was not a trained scientist, but he had a passion for lenses, presumably so that he could closely examine the various fabrics he was buying and selling.
Eventually this passion moved him to develop a rather crude microscope; in all, he made over 500 scopes. With these microscopes, which were actually more like very strong magnifying glasses, he became the first to discover single-celled organisms in water, and he used the microscope to study a myriad of other items that interested him such as bee parts, wood, mold, and crystals.
For Leeuwenhoek, as for other intellectuals of his time, the human body with all its mysteries provided the most fascinating study topic of all. After finding microsopic life in lake water, he progressed to exploring human body fluids like blood and saliva, as well as dental plaque.
After looking at the material he collected from between his teeth under the microscope, Leeuwenhoek wrote the first, and surely most colorful description of living bacteria ever recorded:
"I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number." In the mouth of one of the old men, Leeuwenhoek found "an unbelievably great company of living animalcules, a-swimming more nimbly than any I had ever seen up to this time. The biggest sort. . . bent their body into curves in going forwards. . . Moreover, the other animalcules were in such enormous numbers, that all the water. . . seemed to be alive".
In 1677, his curiosity got the best of him and he took a look at his own semen. He was a bit concerned about the shocking nature of his discovery, and so was quick to point out to his colleagues that the semen had been collected through wholesome conjugal relations, not any immoral means. Leeuwenhoek reported the discovery of said animalcules in his semen. He eventually named these animalcules spermatozoa meaning seed animal.In the 17th century, there was a widespread belief that each spermatozoon contained a fully-formed tiny human being – a homunculus-- just waiting to be planted and nurtured in the female womb. It was said at the time, In each sperm, a person. All that was needed was some time for this little human to develop into a fetus. It took nearly 100 more years for the scientific community to recognize the equal contributions of both the egg and the sperm to the development of a new life.
Leeuwenhoek was an average man who contributed to amazing historic discoveries just by being intellectually curious. Now the question is, what do we do with the outdated word homunculus?
Photo credit: Science Museum UK