The legs

of all quadrupeds are bony, sinewy, and fleshless; and
in point of fact such is the case with all animals that are
furnished with feet, with the exception of man. They are also
unfurnished with buttocks; and this last point is plain in an especial
degree in birds. It is the reverse with man; for there is scarcely any
part of the body in which man is so fleshy as in the buttock, the
thigh, and the calf; for the part of the leg called gastroenemia or is
fleshy.