America is a large, friendly dog in a very small room. Every time it wags its tail, it knocks over a chair.

-Toynbee, Arnold Joseph
  Letter, 26 Oct.

It don't make no difference whether you do right or wrong, a person's conscience ain't got no sense, and just goes for him anyway.If I had a yaller dog that didn't know nomorethana person's conscience does Iwould poison him. It takes up more room than all the rest of a person's insides, and yet ain't no good, nohow. Tom Sawyer he says the same.

-Twain, Mark pseudonym of  Samuel Langhorne Clemens
  TheAdventures of Huckleberry Finn, ch.33.

If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man. Twain The oppressor's wrong, the proud man's contumely, The law's delay, and the quietus which his pangs might take, In the dead waste and middle of the night, when Churchyards yawn In customary suits of solemn black, But that the undiscovered country from whose bourne no traveler returns, Breathes forth contagion on the world, And thus the native hue of resolution, like the poor cat i' the adage, Is sicklied o'er with care, And all the clouds that lowered o'er our housetops, With this regard their currents turn awry, And lose the name of action. 'Tis a consummation devoutly to be wished. But soft you, the fair Ophelia: Ope not thy ponderous and marble jaws, But get thee to a nunneryögo! See Shakespeare 753:74.

-Twain, Mark pseudonym of  Samuel Langhorne Clemens
  Pudd'nheadWilson, ch.16. 1884  The Duke's version of Hamlet's soliloquy, combining elements of other speeches by Hamlet and pieces of Macbeth. TheAdventures of Huckleberry Finn, ch.21.

I cannot bring myself to vote for a woman who has been voice-trained to speak to me as though my dog has just died.

-Waterhouse, Keith Spencer
  On MargaretThatcher, attributed.

To make a start, out of particulars and make them general, rolling up the sum, by defective meansö Sniffing the trees, just another dog among a lot of dogs.What else is there? And to do?

-Williams,William Carlos
  Paterson, bk.1, preface.

You say, as I have often given tongue In praise of what another's said or sung, 'Twere politic to do the like by these; But was there ever dog that praised his fleas?

-Yeats,W(illiam) B(utler)
  'To a Poet, who would have me Praise certain Bad Poets, Imitators of His and Mine', complete poem. Collected in The Green Helmet and Other Poems (1910).