heavens or the sun or the Almighty Creator.”
Like most biologists of his day, Harvey was limited by his equipment. He couldn’t see what was going on at the cellular level. He couldn’t see sperm. He had a magnifying glass, but what he needed was a microscope. And so it is not surprising that the next milestone fell to Antoni van Leeuwenhoek: the man who loved microscopes. Leeuwenhoek did not invent the microscope, nor was he a scientist by training. The Dutchman worked as an accountant for a haberdasher and, later, as Chamberlain of the Council-Chamber of the Worshipful Sheriffs of Delft, which is a ten-gallon way of saying that he tidied the chamber. The post left him plenty of time for hobbies, of which he had just one: grinding lenses and building microscopes. The microscopes Leeuwenhoek built were superior to those of the main maker of the day, and soon they were in demand by members of the Royal Society of London for the Improving of Natural Knowledge, more or less the National Science Foundation of its day. Over time, the Royal Society began publishing Leeuwenhoek’s letters about his findings as well, and he was on his way to a historical, if unpaid, career as the founding father of microbiology.
In 1675, Leeuwenhoek discovered a universe of up-to-then-unknown creatures—bacteria and protozoa, mostly—in drops of stagnant water in a “water-butt” in his yard. He named them animalcules. It is difficult to properly appreciate the wonder and strangeness of this discovery. Think of scientists today discovering Martian life. Leeuwenhoek was appropriately awed. “For me this was among all the marvels that I discovered in nature the most marvelous of all, and I must say, that for my part, no more pleasant sight has met my eye than this of so many thousands of living creatures in one small drop of water.”
Leeuwenhoek bravely turned his instrument upon himself. “My teeth are not so cleaned …” he wrote, “but whatthere sticketh or groweth between some of my front ones and my grinders … a little white matter, which is as thick as if ’twere batter.” He mixed some of this batter with fresh rainwater and looked at a smear under the microscope. Did he find animalcules? You bet your water-butt he did. “All the people living in our United Netherlands,” he concluded, “are not as many as the living animals that I carry in my own mouth.” It is a testament to Leeuwenhoek’s love of biology that he could describe the bacteria in tooth scum as “very prettily a’moving.”
In a further exploration of oral fauna and the limits of spousal patience, Leeuwenhoek headed into the mouth of his wife, Cornelia, and their daughter Maria. “I examined … a little of the matter that I picked out with a needle from betwixt their teeth.” Next he recruited an old man who had “never washed his mouth in all his life” and noted that while his spittle held a normal number of these animalcules, the matter between his teeth held “an unbelievably great company of living animalcules.” Day by day, the foundations of modern oral hygiene took shape under Leeuwenhoek’s lens. He noted the relationship between a “stinking mouth” and “the animals living in the scum on the teeth.” In a three-hundred-years premature dig at Listerine, he observed that while wine-vinegar killed spittle animalcules on contact, it “didn’t penetrate through all the matter that is firmly lodged between the front teeth or the grinders and killed only those animalcules that were in the outermost parts of the white matter.”
While the fellows of the Royal Society were politely attentive to Leeuwenhoek’s oral safaris, they encouraged him to move on to the rest of man’s moistnesses. In particular, they wanted him to examine semen. Perhaps it would be possible at last to view the material of the human soul! Leeuwenhoek refused. “He questioned the propriety of writing about semen and intercourse,” wrote E. G. Ruestow in an