So Very Small
By 
My colleague at Balloon Juice, Tom Levenson, has written another book. Tom is a popular-science writer and has written a number of books on various aspects of science – climate, Newton, Einstein are a few.
So Very Small is particularly relevant to our time. It traces the development of germ theory while also giving an account of how science develops. Tom is on Bluesky, and his comments there suggested to me that the book would be a relative of Microbe Hunters, by Paul de Kruif, a book that was formative for me.
Microbe Hunters, as I recall from decades back, is a series of vignettes about the various scientists who found particular microbes and successfully associated them with disease, sometimes finding a cure or prevention. As a child, I had no trouble imagining myself as one of the scientists: Robert Koch and anthrax, Louis Pasteur’s swan-necked flasks, those who used mercury as a harsh cure for many things, including syphilis.
Levenson uses many of the stories of Microbe Hunters in a different way. Imagine watching your children or neighbors get sick and die and not know why. There are patterns but they do not point clearly to a cause. Some commonality – dead bodies and bad odors suggest that perhaps a malign miasma wafts its way toward the unfortunate. Or they may have been weak to begin with, and something went wrong inside their bodies. Or, of course, God’s inscrutable will.
We see disease through germ theory now, so of course we think about the time we didn’t wash our hands or when kissing someone transmitted a cold. But what if you didn’t know that? That was the situation for everyone through the 18th century and even into the 20th. The history of germ theory parallels the history of increasing expected life spans.
People put cause and effect together and found some things that worked: John Snow shuts down the cholera-contaminated water pump; Pasteur saves a young boy from rabies; and a number of people deliberately scratch detritus from smallpox or cowpox into arms to prevent smallpox. Levenson traces the line from Leeuwenhoek’s discovery of what he called wee beasties to connecting them to disease, which did not come rapidly or straightforwardly.
Levenson tells the story well. His chapters are short and divided further into sections that make for easy reading.
The various pieces of the story have often been simplified or valorized in the telling. That, along with the way science is taught, has developed an idea of single-minded progress in science. But the story of germ theory is a story of good ideas, some of them ignored, bad ideas that sorta worked for the good, and arguments among the scientists.
A schematic of hypothesis formation and testing is taught in schools and has been codified in one of Donald Trump’s many Executive Orders. It is possible, after the fact, to slot the actions of science into that rubric. It is even possible to use it as a guide for those new to science. It can help a non-scientist to understand what scientists do. But it is seldom how science is actually done. Leeuwenhoek discovers his wee beasties in the water, in the scum from his teeth. Who woulda thought that something that small was alive? And they’re kinda cute, in different sizes and shapes.
Later, several people observe that puerperal fever, the fever that kills new mothers, seems to be associated with their caregivers. That is offensive to the caregivers, particularly the doctors whose mission in life is to cure. So there is resistance. The observation of a pattern in the fever’s spread has to fight a social preference. The development of means to prevent puerperal fever did not require knowing what caused it beyond that it was carried on people’s hands and that disinfecting those hands kept women who had recently delivered healthier.
Eventually the pattern of disease joined up with observations of particular types of microbes, like anthrax and cholera. Viruses were a complication that could not be found early on, so some diseases seemed to be exceptions to germ theory.
Science is done by people, often with high stakes. It’s a constant back and forth between observations and ideas of how to interpret those observations. Confusingly, often two or more interpretations fit the observations equally well. They can be distinguished only when more is learned.
Conversely, the facts can all be available, but if they aren’t connected, they are much less helpful.
Science is much more ragged than the easy explantion of the scientific method indicates. People argue and get things wrong. They refuse to speak to each other. They fight about credit for discoveries. Pasteur and Koch had a running feud. But there are things that they find they can agree on. So Very Small shows how those points of agreement slowly accumulate to form germ theory.
When a new disease hit the United States in 2020, the scientific process went through all that in public. People argued and got things wrong. Others went off on tangents, and one of those tangents, m-RNA vaccines, turned out very well indeed. The arguments about who got what wrong are now heavily inflected with politics.
RFK Jr and his minions are in charge of public health, undermining Salk and Sabin and Pasteur and Jenner. Germ theory still stands, and vaccines are still a pillar of public health. Kennedy would put the pump handle back on Snow’s pump because not all the people who get cholera die, and those who don’t must be the stronger for having survived, right?
No, wrong. Every discovery – Pasteur’s unspoiled broths in the swan-necked flasks, the spores that anthrax bacteria form, the molds that kill bacteria – adds to every other to support germ theory and its expression in vaccines. The public got a look at science in action through the COVID pandemic. It was much messier than the easy success stories, some of which Levenson debunks, so many have concluded that there must be something wrong with science. But that is how I’ve done science and others have.
So Very Small is a good book to read now.
Cross-posted to Nuclear Diner