I read this book a while back. The American Bison as a symbol/metaphor was one of the books main themes. The animal was powerful, abundant, and dumb as a rock. There are some interesting bits about Buffalo Nickels in the book. Buffalo nickels were a part of my childhood. I remember studying the powerful beast on the back of these worn weathered coins.
From the book I learned that the actual animal used for the model lived a sickly caged circus-type existence in New York City. Not exactly the symbol of adventure and wide-open prairies it evoked for me as a kid, but a perfect metaphor for the relationship bison had with North American settlers.
These are the output from a little Flash experiment.