The elephant does not sleep standing, as some were wont to
assert, but it bends its legs and settles down; only that in
consequence of its weight it cannot bend its leg on both sides
simultaneously, but falls into a recumbent position on one side or the
other, and in this position it goes to sleep. And it bends its hind
legs just as a man bends his legs.

In the case of the ovipara, as the crocodile and the lizard and
the like, both pairs of legs, fore and hind, bend forwards, with a
slight swerve on one side. The flexion is similar in the case of the
multipeds; only that the legs in between the extreme ends always
move in a manner intermediate between that of those in front and those
behind, and accordingly bend sideways rather than backwards or
forwards. But man bends his arms and his legs towards the same
point, and therefore in opposite ways: that is to say, he bends his
arms backwards, with just a slight inclination inwards, and his legs
frontwards. No animal bends both its fore-limbs and hind-limbs
backwards; but in the case of all animals the flexion of the shoulders