For two follow-up posts on this question, see:
Born July 11, 1899. White is famous for children’s books, style guides, and his work at the New Yorker, but in humor studies, he is probably best known for his introduction to the 1941 book, A Subtreasury of American Humor, which he edited with Katherine White.
The beginning of White’s introduction is one of the most widely known statements about the study of humor, functioning as a witty injunction against the serious study of humor. It reads:
Analysts have had their go at humor, and I have read some of this interpretative literature, but without being greatly instructed. Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind.
But as with many essays on the subject of humor, this statement acts as a clever dodge, what I have taken to calling a “definitional denial.” With a definitional denial, an author says “humor is undefinable”–often in a witty or humorous manner–but this rhetorical move is almost always followed by a definition of various aspects of humor. It is like saying “one can’t define ‘virtue,’ but everyone knows that virtue is this or that, but not the other.” Thus, for another instance, William Dean Howells’s review of Mark Twain’s The Innocents Abroad from the November 1869 Atlantic Monthly begins:
The character of American humor, and its want of resemblance to the humor of Kamatschatka or Patagonia,—will the reader forgive us if we fail to set down here the thoughts suggested by these fresh and apposite topics? Will he credit us with a self-denial proportioned to the vastness of Mr. Clement’s (sic) very amusing book, if we spare to state why he is so droll, or—which is as much to the purpose—why we do not know? 
Practically everyone is a manic-depressive of sorts, with his up moments and his down moments, and your certainly don’t have to be a humorist to taste the sadness of situation and mood. But there is often a rather fine line between laughing and crying, and if a humorous piece of writing brings a person to the point where his emotional responses are untrustworthy and seem likely to break over into the opposite realm, it is because humor, like poetry, has an extra content. It plays close to the big hot fire which is Truth, and sometimes the reader feels the heat.
The world likes humor, but it treats it patronizingly. It decorates its serious artists with laurel, and its wags with Brussels sprouts. It feels that if a thing is funny it can be presumed to be some- thing less than great, because if it were truly great it would be wholly serious. Writers know this, and those who take their literary selves with great seriousness are at considerable pains never to associate their name with anything funny or flippant or nonsensical or “light.” They suspect it would hurt their reputation, and they are right. 
Thus, the humor collection is a “subtreasury,” and thus humor studies confronts some longstanding critical and cultural views about humor as a subject of knowledge. But then again, much can be learned from dissecting a frog, can it not?
 See http://hs.hpisd.org/uploads/45/f69347.pdf
 [William Dean Howells], “The Innocents Abroad,” 24: 146 (December 1869), 764. Kamatschatka (now Kamatchka) is a peninsula in eastern Russia, which had a port prominent in Alaska’s exploration.
 Table of Contents of the book: http://www.modernlib.com/authors/misc/misc/miscMiscToCs/G73Subtreasury.html
(c) Tracy Wuster, 2011-2