"Of All God's Creatures, There Is Only One That Cannot Be Made Slave Of The Leash. That One Is The Cat. If Man Could Be Crossed With The Cat It Would Improve The Man, But It Would Deteriorate The Cat."
The point, which can hardly be repeated too often, is that differentiation is not separation. The head and the feet are different, but not separate, and though man is not connected to the universe by exactly the same physical relation as branch to tree or feet to head, he is nonetheless connected - and by physical relations of fascinating complexity.