The actual quote:
I am convinced that those societies (as the Indians) which live without government enjoy in their general mass an infinitely greater degree of happiness than those who live under European governments. Among the former, public opinion is in the place of law, and restrains morals as powerfully as laws ever did any where. Among the latter, under pretence of governing they have divided their nations into two classes, wolves and sheep. I do not exaggerate. This is a true picture of Europe. Cherish therefore the spirit of our people, and keep alive their attention. Do not be too severe upon their errors, but reclaim them by enlightening them. If once they become inattentive to the public affairs, you and I, and Congress, and Assemblies, judges and governors shall all become wolves. It seems to be the law of our general nature, in spite of individual exceptions; and experience declares that man is the only animal which devours his own kind, for I can apply no milder term to the governments of Europe, and to the general prey of the rich on the poor.
Letter from Jefferson to Edward Carrington, January 16, 1787.
Interesting what gets edited out in these things, isn't it?