Except for the foulness of their bottoms, you would scarcely believe they were animals.
~ Athanasius Kircher, China Illustrated
Kircher is describing apes. It’s not clear that he ever saw one himself. But the notion that toilet hygiene is what separates Sentient Man from Unphilosophic Beast is a nice one. If you’ve ever seen a hippo relieve himself, you know that he is soulless. The cat, on the other hand, suggests sentience, but she only achieves her cleanliness by a filthy maneuver.