A famous anecdote concerning Cuvier involves the tale of his visitation from the devil—only it was not the devil but one of his students dressed up with horns on his head and shoes shaped like cloven hooves. This frightening apparition burst into Cuvier's bedroom when he was fast asleep and claimed:
'Wake up thou man of catastrophes. I am the Devil. I have come to devour you!'
Cuvier studied the apparition carefully and critically said,
'I doubt whether you can. You have horns and hooves. You eat only plants.'

All organs of an animal form a single system, the parts of which hang together, and act and re-act upon one another; and no modifications can appear in one part without bringing about corresponding modifications in all the rest.

At the sight of a single bone, of a single piece of bone, I recognize and reconstruct the portion of the whole from which it would have been taken. The whole being to which this fragment belonged appears in my mind's eye.

Since nothing can exist that does not fulfil the conditions which render its existence possible, the different parts each being must be co-ordinated in such a way as to render possible the existence of the being as a whole, not only in itself, but also in its relations with other beings, and the analysis of these conditions often leads to general laws which are as certain as those which are derived from calculation or from experiment.