In Germany, Scanzoni, Zweifel, and others, apply the forceps differ ently. They place the left blade behind, on the right frontal protuber ance, and the right blade, introduced second and underneath the left, is brought forward to the left lateral portion of the occipital bone. The forceps, therefore, is applied with its lesser curve, not to the occiput, but to the forehead, and directed towards the left thigh of the woman.
We much prefer our method which, when rotation has been made, allows us, in multiparce at least, to extract without a new application of the forceps, while by the German method the forceps being in inverse application, we must re-apply it, or else bring the forehead to the pubes, and deliver the occiput posterior.
8. Position occipito-frontal diameter is in the left oblique of the pelvis, the bi-parietal in the right oblique. The occiput is behind and to the right, at the level of the right sacroiliac synchon drosis, the forehead in front and to the left, at the left cotyloid cavity; the right side of the head is behind and to the leit, the left side in front and to the right. The forceps is applied symmetrically to the head, and asymmetrically to the pelvis, an oblique application. The left blade is first introduced to the left and behind, on the right side of the head; the right blade, directed first behind, is brought forward, by the spiral movement, to the left side of the head. The lesser curve is applied to the forehead, and directed towards the left thigh of the mother, as in the position O.I.L.A. (Fig. 102.) Traction is made first downward, to bring the head to the perineum, and then rotation is made from right to left, to bring the occiput under the pubes. If rotation is impossible, we resort to Pajot's method, and when the forehead is under the symphysis, we extract the occiput posterior.
We see then that the rule, requiring the lesser curvature of the forceps to be directed towards the side of the head which we intend bringing under the pubes, is not absolute, is true, indeed, only when in posterior positions we wish to deliver the occiput posteriorly. Then it is towards the forehead that the lesser curve is placed; but when rotation is to be attempted, the forceps is applied according to rule, only in anterior posi tions. In fact, in the positions 0.I.L.A and O.I.R.A., the lesser curve
is directed towards the occiput, only in 0. I.L. A., this curve points towards the left thigh, since the occiput is in front and to the left, while in 0.I.R.A., it looks toward the right thigh, the occiput being in front and to the right.
In the positions 0.I.L.P and 0.I.R.P., on the contrary, the occiput is posterior, and the rule is not applicable, for if we wish the lesser curve to be directed at the outset towards the occipat, we would be obliged either to grasp the head irregularly, that is to say, from one frontal pro tuberance to the opposed portion of the occiput, as in transverse posi tions; or, if we wished to grasp the head regularly, we would have to apply the forceps with left blade to right, and right to left, which is in admissible. The forceps, then, is applied as though the occiput were in front, and the lesser curve is at the forehead, pointing towards the right thigh in 0.I.L.P., and towards the left in 0.I.R.P. The head is then rotated and brought under the symphysis, and the forceps is in inverse application. In case of a multipara we at once deliver; in case of a primipara the blades are removed, and re-applied directly to the head.
If in a few words we resume the principles applicable to the placing of the blades: In anterior and transverse positions, the first is the posterior blade, and the second is applied over the occiput, occiput to left, left blade, to right, right blade. In posterior positions, the first blade behind, the second over the side opposed to the occiput, occiput to left, right blade, occiput to right, left blade.
The higher the head, the greater the necessity of bringing it down before attempting rotation. If we use Tarnier's instrument, never attempt ro tation with the traction-rods alone, but unite the four branches (those of traction, those of prehension) in one hand, and then try. This, it will be remembered, is one of the objections we made to Tarnier's instrument.
The following table shows the different applications of the forceps in vertex presentations.