Some few persons only are double-crowned. The bones of the head are flat, thin, devoid of marrow, and united with sutures indented like a comb. When broken asunder they cannot be united, but the extraction of a small portion is not necessarily fatal, as a fleshy cicatrix forms, and so makes good the loss. We have already mentioned, in their respective[1] places, that the skull of the bear is the weakest of all, and that of the parrot the hardest.