Note 252 — Chapter VII · THE GODS AND THE SONS OF GOD
Reading edition
They were apparently masters of the extremely difficult operation of trepanning, which they probably performed in cases of accidents. That their trepanning was successful is proved by the number of skulls that have been found, the bones of which bear evidence of having been trepanned and having healed up. See Professor Keith, The Antiquity of Man, p. 21; also Robert Munro, Prehistoric Problems, pp. 203–205.