The general rules for application are identical to those of the forceps, the difficulty, of course, being greater, and frequently the entire hand must be inserted into the vagina.
Locking.—The same rules apply to this procedure as to the forceps, although greater care, if possible, is necessary, for the cephalotribe being more massive than the forceps, the risk of injury to the maternal parts is greater.
Crushing.—As Pajot well says the responsibility of the assistant who steadies the head is here great, for the classic cephalotribe being very nar ro•, the head tends to slip and the operation may on this account fail. Further still, the assistant is able to appreciate how the head has been grasped.
The process of crushing should be slow and intermittent, and should be kept up until the handles of the instrument have been brought into con tact. As the head collapses and the cerebral matter escapes, compression must be more energetic, or else the instrument will slip at the first trac tion.
Extraction.—After an interval of a few minutes, the cephalotribe should be seized in both hands, and rotated so as to bring the lesser curve of the instrument towards one or another thigh of the mother. (Fig. 156.) This movement aims at bringing the crushed . diameter of the head into the conjugate—that is to say, the most contracted diameter of the pelvis.
The head having been crushed in one direction, elongates in the other, and this elongation is in the conjugate of the pelvis. Tractions are then made, and these must be slow, sustained, combined with lateral move ments. Ordinarily, the instrument rotates itself as the head engages, and we must favor this spontaneous rotation. The head once in the cav ity, rotation in the inverse direction is made, and thus the lesser curve of the instrument is brought under the symphysis. Traction, even as with the forceps, should always be made in the pelvic axis, and during delivery the perineum should be as carefully watched. The head once delivered, the body follows quickly, except in case of great contraction. " We may then," says Pajot, "apply the cephalotribe on the thorax, or else, by traction on the body and rotation of a shoulder under the syinphysis, we may be able to hook a finger in the axilla, bring down an arm, and thus deliver." Each of these periods may offer difficulties which render cephalotripsy one of the most delicate operations in obstetrics. It is often extremely
difficult to place the blades, and it may be necessary to attempt the pas sage several times before our efforts meet with success. The irregularity of the pelvis and the narrowness increase the difficulty, whence the neces sity of proceeding slowly, pushing the blades in deeply, making sure that the head is well grasped. A capital point to be remembered is, as Pajot points out, the necessity of carrying the handles as far backwards as is possible, in order to assure grasping and crushing of the base of the skull.
Bailly's instrument is, we think, the one which best enables us to ac complish our aim, owing to the breadth of the blades and the greater concavity. The head is thus grasped the better, and cannot so readily escape from the instrument. Where the pelvis is greatly contracted, however, if the blades are not carried sufficiently backwards, their ex tremities touch the posterior pelvic wall, and the projecting sacro-verte bral angle. Here it is that repeated attempts at application of the blades are necessary, and however gently these are made, the risk of injury to the maternal parts is greatly enhanced. The danger from cephalotripsy, therefore, increases greatly in direct proportion to the degree of pelvic deformity.
Generally, with Bailly's cephalotribe, locking is not difficult, but the same does not hold true of the classic instrument, on account of the nar rowness of the blades.
During crushing, slipping of the head is more likely as it is badly grasped and movable. The chief difficulty, however, is to crush the base of the skull. With Bailly's instrument, whenever it can be used, we are able to obtain most readily complete destruction of the base. During ex traction, the chief thing to guard against is slipping, which may cause such injury to the maternal parts. It is to avoid this risk that Tarnier and Bertin have proposed, after a few attempts at extraction, if the head does not engage, to resort to podalic version. The objection we would make to this proposal, is that the uterus is often retracted on the fo3tus, and that version is hence impossible without running great risk of rup turing the uterus. Further still, version is far from being practicable in every pelvis.