This book is an utterly fascinating slice of history and perspective from a distinguished American bacteriologist writing in the 30’s. I picked it up looking for a historical piece focusing on rats, but was equally delighted to discover that the book is better described by its alternative title: “Being a Study in Biography, which, after Twelve Preliminary Chapters Indispensable for the Preparation of the Lay Reader, Deals with the Life History of TYPHUS FEVER.”  
Whew! There was still some fantastic writing on rats though, so it well deserves a place in the book club.

This book is an absolute classic of science literature. Zissner set out to write a “biography of typhus”, an attempt to stick his middle finger up at two genres of writing he absolutely detested. First was the popular biographies of the time, which used Freudian armchair psychoanalysis and post-mortem attribution of new mental health classifications to rewrite the lives of the famous into what was essentially the 30’s version of ‘scandalous clickbait’. As Zissner put it: “Great men are being reappraised by their endocrine balances rather than by their performances.”

Second was what was regarded as “popular science”. At the time, intellectuals were expected to stay in their lane. For a scientist to foray into making public statements on the arts (including writing outside of journals) or politics, was something to be mocked. Zissner held what is now regarded as a very modern view - that science can only excel when a more holistic view is taken, looking at the broader picture of social and historical impact, understanding the past and present influences and using that knowledge to guide decision into the future.
Zissner wrote in a witty, tongue-in-cheek style that was as far as possible from the ‘popular science’ of the 1930’s. Ironically, his style and structure came to define the genre he hated so much - it reads very much like modern pop science! 

Rats as disease sources
Zissner writes 12 chapters on different related topics before tackling typhus fever directly, with our interest being Chapter 11: “Much about rats - and a little about mice”.
Rats are relevant to the story as one of the carriers/reservoirs of some species of bacteria responsible for typhus fever, alongside other animals such as rabbits, dogs, sheep, guinea pigs, mice, and ‘native Mexican rodents’. While the rat gets a poor reputation as a disease vector, it’s actually fleas and lice who transmit it between rats, and between people. Interestingly, much of what is historically regarded as typhus was likely not transmitted via rats at all, but between humans sharing head and body lice, and some forms are passed down parent-to-offspring in ticks.

Rat origins
There was a lot of interesting information to be found in such an old book, some of it which has been updated since. Zissner discusses evidence for the timeline and spread of rats across the continents. Despite rats being recorded in the fossil record in Europe during the Pliocene Era, they seem to have disappeared after the glacial period, before Rattus rattus (the black rat) came from the East between 400 and 1100 A.D. Rattus norvegicus (the brown rat, the species of our domestics) came later, spreading across land and sea via trade routes, likely originally from Mongolia. The brown rat outcompeted and displaced R. rattus in all areas but dockyards and places where being lithe and agile climbers gave the advantage.

Nomenclature
At the time, rats were considered the same genus as mice, so what we now call R. rattus was classified as Mus rattus, with R. norvegicus dubbed Mus decumanus. Later the brown rat’s origin was falsely attributed to Norway, hence the taxonomic change. R. norvegicus was also called the common rat in many areas. When the rat reached Britain it was called the “Hanoverian Rat” due to displeasure with the House of Hanover at the time, and in Western Europe they were called the “French Rat” at first - anything new or unpleasant was blamed on the French at the time, syphilis being another example of that trend, when many nearby countries called it “The French Disease”, or whichever other country was the most disliked during the initial outbreaks.
 

Rat treatment and perception in history
Zissner noted a list of historical references to rats that indicated revulsion. Even as a rat lover I can understand the hatred, rats have long eaten and spoiled the hard earned stored grain and other food supplies of humans, to the point where the ancient Greeks theorised that mice (the ancient Greeks had no separate classification for rats and mice, so either they were seen as the same thing, or rats were not present at the time) were formed spontaneously in areas where too much grain was stored in the one place!
To quote Zissner on rats across cultures: “In ancient Palestine, the Jews considered all seven mouse varieties unclean, and as unsuited for human nourishment as were pigs. The worshipers of Zoroaster hated water rats, and believed that the killing of rats was a service to God. It is also significant that Apollo Smintheus, the god who was supposed to protect against disease, was also spoken of as the killer of mice, and Saint Gertrude was besought by Bishops of the early Catholic Church to protect against plague and mice.”
He also references a severe plague in Frankfurt, Germany in the year 1498, during which a royal attendant stood on a bridge paying a pfennig for every rat brought to him, cutting their tails off and throwing the bodies in the river much like modern bounty collectors use scalps and tails. In later years, an annual tax of five thousand rat tails was supposedly levied on the Jewish community of Frankfurt. This, and the religious associations with rat killing, shows that the association between rats and disease was well established at the time.

Insights
Zissner spoke of rats as being more like man than any other creature, with their/our tendency to breed ourselves into a plague of self destruction, ravage the land and consume our resources at an unsustainable rate. He also pointed out that men were equally responsible for carrying the disease to new areas and infecting the local rodents, as much as the other way around!
If I’ve learned nothing else from reading this book, it's that Hans Zissner was a sharp man with incredible vision and an absolute smartass, someone I would very much love to have had a cuppa with.
If you enjoy medical history and snark, this makes for a great read. Some of the statistics for disease casualties in war are staggering (truly, sanitation wins wars, not soldiers or generals) and it’s a truly fascinating journey to read, with some great insights into the perception of rats and a few good laughs.

One sentence summary: Snarky old scientist talks about how rats are widely and historically hated, but probably weren’t as responsible for typhus outbreaks as people think.
Worth reading if: You like medical history, especially in old-world wars.

By Grover Greenfield

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