Polysyndenton is the repeated use of conjunctions in cases where they might be omitted. In "Corn-pone Opinions," Mark Twain uses this to specific effect, adding the word "and" in places where a comma or semi-colon might be appropriate. This allows the essay to sound more carefree and friendly, rather than sounding controlled and stolid. For example, Twain remarks on his friend who used to "preach" to Twain, explaining his unique outlook on life:
He was a gay and impudent and satirical and delightful young black man -- a slave -- who daily preached sermons from the top of his master's woodpile, with me for sole audience.
The use of "and" in this sentence punctuates each of the descriptive words, showing the reader how much Twain admired his friend, and only after the word "young" is the friend's race and social status explained. In this way, the punctuated positive descriptions affect the reader -- indoctrinated with the general anti-black sentiments of the time -- before the potentially-negative admission of his race and status are mentioned. Each "and" allows the word after it to be heard and absorbed, negating the negative effects of "slave."
Another example comes when Twain explains his friend's opinion that if he hears where a man "gets his corn-pone" (where he lives, works, and eats) will inform of the man's opinions, even if they are unknown. This means that a man usually derives his opinions from his living area, where he must fit in and be accepted; if he goes contrary to the common opinion, he might be expelled. Twain, thinking on the possibility of an opinion that is fully objective, comments:
It may be that such an opinion has been born somewhere, at some time or other, but I suppose it got away before they could catch it and stuff it and put it in the museum.
(Twain, "Corn-pone Opinions," paulgraham.com)
Here, the use of "and" is for comedic effect; the "objective opinion" cannot exist in Twain's mind and so if it had, it would have been subdued (caught and stuffed and put in a museum) by the brutal relativism of common opinion. In this manner, the essay becomes more intimate with the reader, instead of sounding bombastic or preachy.