I speak French with timidity, and not flowingly—except when excited.
When using that language I have often noticed that I have hardly ever been
mistaken for a Frenchman, except, perhaps, by horses; never, I believe, by
people.

(Mark Twain [Samuel Langhorne Clemens] (1835-1910), U.S. author. (1881).
"Dinner
Speech in Montreal," p. 779, Mark Twain: Collected Tales, Sketches,
Speeches, & Essays, 1852-1890, 

http://www.poemhunter.com/quotations/famous.asp?people=Mark+Twain+[Samuel+Langhorne+Clemens]&p=5