On the other hand, if we endeavor to apply the forceps symmetrically to the pelvis, one blade, in case of vertex presentations, is applied over the forehead, and the other over the occiput; in case of face presentation, one over the chin or the face, the other over the occiput, that is to say, not to mention the possible lesions on the face, in the last instance parti cularly, the head is seized in its greatest diameters, and extraction will be all the more difficult.
Hence, in France, we have recourse to another method: The applica tion is made obliquely both to the head and to the pelvis--that is to say, without seeking to seize the head exactly in the bi-parietal diameter, the instrument is applied in such a manner, that the blades are in a diameter intermediate between the bi-parietal and occipito-frontal in vertex pres entations, between the bi-parietal and the fronto-mental in face presenta tions. In a word, the head is grasped obliquely posterior to the parietal region of one side, and to the frontal of the opposite side. The head is thus seized obliquely, both to it and to the pelvis, in an irregular manner, but we believe this preferable to the German fashion ; for although the diameter in which we grasp the head is not the shortest, it is at least not as long as the occipito-frontal or the occipito-mental.
Finally, when the head is at the superior strait, we can only exception ally grasp it in the bi-parietal diameter, but must in an oblique.
The accoucheur has exact information in regard to the way in which the head has been grasped. When it has been seized symmetrically, the blades, when the instrument is locked, are but little separated at the level of the handles, but are notably so when the head has been grasped irreg ularly or asymmetrically. Then we must be all the more on the watch against slipping.
In many cases, however, we admit that it is impossible, notwithstand ing every attempt, to grasp the head symmetrically ; and, as it were of themselves, the blades are applied in the intermediate diameter, for it is here there is the most room.
3. The posterior Blade should usually be inserted first.—Where it is resistance of the perineum which calls for interference, the occiput is usu ally to the pubes; where the head has rotated backwards, we may apply the forceps directly, although usually the application must be oblique. One of the most frequent calls for interference is absence of rotation, the head being often transverse, but usually oblique, since these positions, as we have seen, are the fundamental, the others being simply varieties or consequences. One side of the head, hence, is in front, and the other is behind, and in order that the head may be grasped symmetrically at the sides, one blade must be directed backward, and remain posterior when the instrument is locked ; the other must be directed anteriorly and remain there. The posterior blade is ordinarily introduced first, and
placed at the posterior extremity of the bi-parietal diameter. This rule, however, is not at all absolute; there are many exceptions, and, as Cazeaux well says, " it is habit and discernment of the accoucheur which guide him at the bedside in the insertion of the one or the other blade first." 4. The male or left Blade is always held in the left Hand, and is always applied to the left Side of the Pelvis. (Fig. 82.) The female or right Blade Is always held in the right Hand, and is always applied to the right Side of the Pelvis. (Fig. 83.)—This is about the only rule without an exception. The forceps, indeed, is so constructed that it ought not and cannot be applied otherwise. But the rule is not so absolute in regard to the hand which ought to hold the blades. Hatin, indeed, has proposed introducing both blades with the same hand. " One hand is introduced, by preference the left, up to the fundus, or at least as far as the fenestrie must pene trate. The first blade having been passed along this guiding hand, this, without being removed, is simply turned to the opposite side of the festal head, in order to receive and guide the second blade." This method, which should be reserved for very exceptional cases, is really far inferior to the ordinary and classic method, and the above rule is almost abso lute: Right blade, to the right, right hand; Left blade, to the left, left hand.
5. The Hand intended to guide the Blade, should ever be introduced first.—This rule is perhaps more absolute still than the preceding. The object is both to protect the maternal and infantile parts, and to guide the blade. We cannot, therefore, be too careful, and if, when the head is at the vulva, or at the level of the inferior strait, one or two fingers, between the head and the vaginal walls, suffice, the palm of the hand must always be introduced when the head is higher up, and the thumb as well when the head is at or above the superior strait. In the latter in stances, indeed, the ends of the fingers must be within the uterus, between the head and the cervix, to be sure not to seize the cervix between the blades, and to be sure that we are in the uterus and not in one of the culs-densac. It is imperative, also, whenever the instrument is introduced within the uterus, to cause the fundus to be depressed, and the head steadied by an assistant, in order to bring the cervix and the head as near as possible to the operator.