Bertha Mason (Jane Eyre; Brontë, C.)

, the first wife of Mr. Rochester.

I seriously don't think she was insane when Rochester married her. She may have become insane since, but only as a consequence of being locked up.

How was she mad? From what I could tell, she had a temper, some form of alcoholism, and a high libido. This was considered improper and outrageous for a woman in the story's Victorian setting. She was thus promptly declared mad and locked up.

The animalistic behaviour occurred only afterward, clearly as a consequence of her imprisonment. What about her animalistic appearance? Well, what do you expect from being locked up for decades in a barren room, denied material comforts? And thects of violence and sabotage whenever she escaped? What do you think, Rochester? Did you think the wife you imprisoned in a barren room in her own own for decades would smile and shake hands with you?

Jane, you will not have a happy life with Mr. Rochester. He may be happy to be led around by you now because he's missed you, but be sure that he will gradually lose tolerance for his dependence on someone of lower status, just like he refused to be led around by the servants.

(By the way, the Deus Ex Machina to bring Jane back to Thornfield... Really, Brontë?)

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EDIT (20th July, 2012):
"Bertha Mason's Madness in a Contemporary Context" (Iwama, M., 2003) (http://www.victorianweb.org/authors/bronte/cbronte/iwama8.html) explains that the conditions Bertha is placed under, and the other characters' attitudes toward her, were considered deplorable even by Victorian standards.

Why did Rochester, with his considerably deep pockets, not send Bertha to receive proper treatment? Combined with the secrecy surrounding Bertha's existence, to the extent that only her caretaker/jailor Grace Poole knows who Bertha is, I think it is very clear that Rochester's intent with sequestering her is to conceal her and his relationships to her, in order to avoid the anticipated shame and loss of face.

Bad boy! Sit!

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EDIT (6th February, 2013):
Having read Wide Sargasso Sea (Jean Rhys) in the intervening months, I highly recommend anyone who has read Jane Eyre to do so.