I've heard men called many things but....(metaphor)

"Some men are almost rhinoceroses; they don't respond properly to conditioning." p. 90

A little confused by this metaphor in that I have never tried nor heard of anyone trying to train a rhinoceros. I think this might be Huxley's attempt to avoid the ol' chiche: "Stubborn as a mule." Now that, I can relate to as I, and many men have been called mules. "Maybe we should ask for directions?" "No, I know exactly where we are." "Really? Then why has this 2 hour trip been turned into a 4 hour trip?" But, in general, I think this metaphor serves to point to an event later in the chapter hearing that he would be sent to Iceland. The metaphor explains why in that Bernard is an individual in a society that doesn't accept diversity. He thwarts normal social behavior and is considered "odd" and therefore deemed a threat to the perfect society so he must be isolated. A bit harsh, I think.