Quite as interesting is the full quote: Triste est omne animal post coitum, praeter mulierem gallumque; "except the woman and the cock (= rooster)".

This is, I am now led to understand, by Galen (c. 130-201), the great physician to the emperors; though until I did a Web search just now to find the exact work, I had thought it was by Aristotle (who would of course have been read in Latin translation for most of history); and I have also seen it given to Ovid. But Kinsey goes for Galen.