Sentence:  Let that be as it may, as my purpose is to do exact justice to every creature brought upon the stage of this dramatic work,—I could not stifle this distinction in favour of Don "Quixote'''s horse;—in all other points the parson's horse, I say, was just such another,—for he was as lean, and as lank, and as sorry a <WSD>jade</WSD>, as HUMILITY herself could have bestrided. 
Meaning of the word marked with <WSD> tags:  A horse too old to be put to work.