Afterword to Mrs. Frisby and the Rats of NIMH. From the Penguin 1994 edition.
Poor Rats! They might be the least popular of all animals, both in real life and as characters in fiction. So how the American author Robert O'Brien came to adopt them as heroes of his book is best explained in his own word:
"It happened that a friend of mine was seriously ill and was sent to the NIH (National Institute of Health) for treatment. He was required to take a daily walk, so when I visited him a few times we walked together around the NIH grounds--numerous buildings set in a park.
"One large, low building was unlike the rest, and when we asked, we were told that it was the animal production laboratory, where rats, mice, rabbits and guinea pigs are raised for use in scientific tests. The attendant we talked to said that though they had no trouble with the other animals, the rats somehow managed to get out of their cages at times. He added that when energy and intelligence were required in a test, the scientist much preferred 'wild rats' over the docile laboratory-bred variety. I am quite sure it was this conversation that put the Rats of NIMH into the back of my head--where they stayed for several years before emerging as a story."
But however energetic and intelligent, there is still a problem in making rats the heroes of any story. Twitching noses, yellow teeth and rapid darting movements can be alarming at first glance, although tame white rats have often been much loved pets. Wild rats also carry diseases, and have been blamed for spreading the Plague that once wiped out so many families in Europe. Although--as Nicodemus points out--rats 'never spread as many diseases as people do themselves', they are still feared as well as hated for their habit of stealing food.
In Robert O'Brien's story, rats have a much better image. Instead of behaving like rodents, they speak English, get married, have human names, and sit down on benches in order to read books. When young Isabella comes into a room, she is carrying a pencil and 'looking at some papers as she walked'. This is no hurrying, scurrying rat: the picture is closer to an attractive, educated young woman. Just as Anna Sewell's noble horse character Black Beauty talks like a sensitive young Victorian, Robert O'Brien's rats come over as decent, family- loving humans in rat disguise. It is easy for us to side with them in their tussle against their worse oppressors: human beings in their own skins.
Readers often enjoy books that show the human race in an unflattering light. We always learn somthing from such fiction, ending up with a better view of our own faults as seen from the point of view of smaller beings. Mrs. Frisby and the Rats of NIMH also teaches us to be more tolerant of other forms of life on this small planet: a lesson even more relevant now than it was in 1971, when the book first came out. All creatures play a part in our environment: scavengers such as vultures and jackals who, like rats, are also often given bad parts in stories, in fact have an important job to do clearing up after other animals.
We also know how clever and ruthless humans are when pursuing their own ends. Any animal that still manages to give us a good fight cannot help winning our respect. So the rats' escape from the laboratory and Mrs. Frisby's last-minute rescue from her cage are both nail-biting tense, given the odds against them. No one grudges the rats their happy ending, finally escaping from an experimenter who simply wants to use them for cold-blooded scientific research. It may still be difficult for most of us to change our minds permanently about rats after finishing this story. But no reader will ever feel the same about field-mice again, having come across such a great-hearted little creature as Mrs. Frisby herself.
It is always sad when a good story ends, especially when there are still some details that remain unclear. Which rats did not make it and how successful was the new civilization at Thron Valley? Fortunately, two sequels are available, answering these and other questions and written by the author's daughter Jane Conly, so readers can discover more about Justin, Brutus, Timothy Frisby and Jeremy the crow. This means there are still plenty of exciting adventures to come, again often to do with the continual struggle between animals and humans for the world's remaining resources, so vital for all forms of life.