Decapitation has now given way before Caesarean section; but the decapitator, little altered since the days of Celsus, still finds a place in surgical instrument catalogues. Paul and Aetius both mention division at the neck, but do not describe a special instrument. A ring knife for dismembering the foetus has already been discussed among the cutting instruments; but this seems to be a different variety with a handle, which it is convenient to discuss in proximity to the embryo hook. Pl. L, fig. 2 shows a knife on this principle in the Bibliothèque Nationale. _Cranioclast._ Greek, πίεστρον, ἐμβρυοθλάστης, θλάστης; The cranioclast is mentioned by Hippocrates (ii. 701). Σχίσαντα τὴν κεφαλὴν μαχαιρίῳ ξυμπλάσαι ἵνα μὴ θραύσῃ τῷ πιέστρῳ καὶ τὰ ὀστέα ἕλκειν τῷ ὀστεουλκῷ. 'Opening the head with a scalpel, break it up with the cranioclast in such a way as not to splinter it into fragments, and remove the bones with a bone forceps.' The nature of the cranioclast is pretty well indicated by this passage, and in Galen's Lexicon we find πιέστρῳ defined as τῷ ἐμβρυοθλάστῃ καλουμένῳ. I give drawings from Albucasis of a 'forceps to crush the child's head' (Pl. LI, fig. 3). _Cephalotribe._ Whether or not the instrument last described was used also for the operation of cephalotripsy, or whether there was a special instrument, we cannot say, but it is certain that the operation of crushing the head and delivering the child without removing the bones was practised. In Aetius (IV. iv. 23) cephalotripsy is thus described: 'But if the foetus be doubled on itself and cannot be straightened, if the head is presenting, break up the bones of it without cutting the skin. Then to some part of it fix on a traction hook and make traction, and the legs becoming straightened out we get it away.' Though there is an essential difference between the operations of cephalotripsy and cranioclasie there is no essential difference between the instruments necessary for carrying out the same, and it is possible that the instrument used may be the same as the last. The cephalotribe figured by Albucasis is not essentially different from his cranioclast (see Pl. LI, fig. 4). _Midwifery Forceps._