"YOU dirty rat." Everybody knows that screen gangster James Cagney uttered these words in one of his myriad movies. Or did he? Apparently not, say the authors of They Never Said It, a recently published compendium of oft-quoted misquotes and misattributions.

In fact, the authors say in their exhaustive--even tedious--catalogue of quotes, Charles Boyer never invited anyone to the Casbah. Sherlock Holmes never chided his sidekick with the words, "Elementary, my dear Watson." And Will Rogers never said he never met a man he didn't like.

They Never Said It

By Paul F. Boller, Jr. and John George

New York: Oxford University Press, 1989.

159 pp., $15.95

Boyer's statement was a fabrication of his publicist, Holmes' a pure fabrication and Rogers an inaccuracy (What the comedian actually said, according to George and Boller, was, "I joked about every prominent man in my lifetime, but I never met one I didn't like.")

Half-serious, half-mocking in tone, the book is a Bartlett's of botches that cannot decide whether it wants to be a reference book for hack writers--footnotes and all--or a coffee-table text for the literati--hence the discussion of "quotesmanship," with the politically-correct parentheses presenting quotes-woman beside quotesman.

Some of the quotes on which the authors cast aspersion are phrases that everyone knows to be inaccurate. Any one who thinks that Humphrey Bogart really said "Play It Again Sam" hasn't seen Casablanca. If you think the Bible is the home of the maxim "God helps those who help themselves," then God help you.

But other comments that the authors note are more obscure. When was the last time you heard these lines, incorrectly attributed to poet Ogden Nash: "Shake and Shake the catsup bottle./ None will come, and then a lot'll"?

One gem in this book is the explanation of Barry M. Goldwater's supposed declaration that "Where fraternities are not allowed, communism flourishes."

This misquote, the authors, say, is the fault of a reporter at the Baltimore Catholic Review, who confused the senator's statement that he did not understand why Harvard students were attracted to Keynsian economics and a later mention of the "value of college fraternities." The reporter apparently mistook the word "Keynsian" for "communism."

BUT They Never Said It goes a little gung-ho on detail. Some things are better left unsaid. Although comparing the misquotes with the real thing is fun, reading descriptions of how statements got mangled tends to get boring.

And then, of course, there is the irony of including such misstatements as "Too much checking on the facts has ruined many a good news story" (attributed to Roy Howard). Chief Justice Warren Burger may have made a mistake in attributing the statement to Howard, but there's no mistaking the element of truth in the notion--an element that Boller and George seem to overlook. They've checked out their quotes in a scholarly way, but somehow they lose the pizazz of the lines as they go along.

The authors of the book also seem to be a bit too trusting--if someone says they never made the statement, then obviously they did not make it. Philip Sheridan, for instance, is often credited with having said, "The only good Indian is a dead Indian." The quote stems from an account of the meeting between Sheridan and Commanche leader Toch-a-way. Sheridan denied having made the statement, but who would not--after the fact?

Unfortunately, although the authors of They Never Said It explain these circumstances, they do not really suggest that Sheridan might be lying. They may be trying for objectivity, but given the book's title, the reader is sure to conclude that Sheridan's side is the one to pick. This lack of clarity is disturbing, considering that many of the book's statements have to do with politicians like Nixon, Stalin and Lenin--that is to say, people who should not be taken at their word.

Then again, as Harry Hopkins never said, "The people are too dumb to understand."