B. The Head is only partially engaged at the Superior Strait.—In this case the obstacle to the engagement of the head is usually due to a con traction of the pelvis or to prolapse of a foetal part. The head is almost always transverse; direct anterior and posterior positions are not possible. The oblique may be met with when the contraction is moderate, and the head not very large. The transverse position is the rule, and it is hence usually impossible to grasp the head regularly; and to endeavor to apply the forceps, according to the German method, parallel to the pelvis, is to grasp the head from occiput to pubes, and consequently to increase the obstacle. We must, therefore, act as in transverse positions with the head in the cavity, seize the head by one frontal protuberance and the opposed side of the occiput.
The choice of the anterior and the posterior blades is here again subor dinated to the side where the occiput lies.
In the position O.I.L.T., the head is grasped between the posterior portion of the occipital bone and the anterior portion of the forehead; the left blade is inserted first, to the left, and applied to the left portion of the occiput, the right blade is inserted second, to the right and behind, then brought forward by the spiral movement over the right frontal pro tuberance. The lesser curve is directed towards the left thigh of the mother. The head is grasped irregularly. At the outset traction is made downwards, rotation occurs from left to right, and extraction with the occiput to the pubes.
In the position 0.I.R.T., the right blade is inserted first, behind and to the right, over the right side of the occipital bone; the left blade, in * serted second and behind, is brought forward over the left frontal protuberance. We must, therefore, either cross the blades, or else use Stoltz's method. When the forceps is locked, the lesser curve points to the mother's right thigh; the head is grasped irregularly. Traction is first made downward, to engage the head, and to bring it down as far as is possible, then it is rotated from right to left, and extracted with the occiput to the pubes.
The capital point, in order to thoroughly grasp the head, is to intro duce the blades deeply enough. In such cases the pivot of the instru ment is almost at the vulva. The hand, then, which is to guide the blade, must be passed deeply between the head and the cervix to protect the maternal parts, and the head must be steadied from the outside by an as sistant, when the blades are being placed, for it tends to escape above the brim.
Traction must be made in the axis of the pelvis, and this, as all au thorities agree, is the true difficulty. To remedy it, Pajot devised his method, and Hubert, Fabri, Morales devised the perineal curve of the forceps, which Tarnier himself adopted in his first model.
Tarnier tries to solve the problem by placing the woman on the side, in order to be able to make traction as far back as possible without being inconvenienced by the side of the bed, and he makes the woman resume the dorsal position as soon as the head has reached the cavity. But it is not only the border of the bed which is in the way, but the perineum itself, against which the blades press as soon as the forceps is carried enough backwards. Now, if it is difficult, if not impossible, to carry the classic forceps far enough back, it is even more so Tarnier's, the indicator needle of which is made to tell us the direction in which traction must be made. In these cases, the indicator calls for that which is impossible, for we cannot make traction far enough back, and it is only, indeed, when the head is below the superior strait that the indicator can give real indi cations, for then we can fulfill them. Such an ardent advocate of Tar nier's forceps as is Pinard, is obliged to admit that, in oblique applica tions, the head being above the superior strait, traction by means of the instrument is not perfect, for the perineum interferes with its being placed in the pelvic axis occupied by the head.
Now this is one of the marked advantages of Pajot's method. It is said that, in this method, the forceps does not act as a tractor, but as a lever. Of what use, however, here mathematical miles, which are at the best simply problematical, since the pelvic axis changes with each woman, ac cording to the form, dimensions, and deformities of the pelvis? The main point is to make the head descend with the least damage to mother and to child. Whether, then, the forceps acts as tractor or as lover, the best method is that which permits the head to pass easily and rapidly through the superior strait, and it is admitted that in many cases this is possible by Pajot's method, where simple tractions fail. Further, in these eases, the lateral movements, carefully made, are of great utility.