Drinking, when we are not thirsty and making love all year round, madam; that is all there is to distinguish us from other animals. – Pierre De Beaumarchais

The fatter the flea the leaner the dog. – Proverb

I have been studying the traits and dispositions of the “lower animals” (so called) and contrasting them with the traits and dispositions of man. I find the result humiliating to me. – Mark Twain, Letters from the Earth, 1907

It often happens that a man is more humanely related to a cat or dog than to any human being. – Henry David Thoreau