His heart is as firm as a stone; yea, as hard as a piece of the nether [millstone]. Which must be understood not of the substance but of the qualities of it, being bold, courageous, undaunted, and unmerciful; which is true both of the whale and crocodile, and particularly of the crocodile: Aelianus relates of one sort of them that they are unmerciful, though elsewhere , he represents them as fearful.
De Animal. l. 12. c. 41. Ibid. l. 10. c.