pubis. the head FACE PRESENTA ot were thrust back left foot. If, in such which, in addition to a face prese Fig. 79. very the absence of a in either case, the same circumferences of the head are. the planes through which they are to be transmitted magnum of the occipital bone being nearly equidista and chin, and situated on one side of the oval, the and hazards of these labors are attributable, rat the articulation by which the neck and head. the form of the head itself, when advancing The nature of this articulation is such, th cannot take place so well as flexion; her occipito-frontal diameter is not effected and the consumption of much time. Let the reader figure to himself th child, urged on in labor by powerf its expulsion with the face in adv the head is pressed against the pulæ, which could not be the c backwards, like a bow, whil curved in the opposite direct curve, on which, in conser much of the expulsive fo power may be as great? effect than in a commo pended in reproducir elasticity of the two in some measure, a tions of labo from th Let th Herges, rch. which it passes in reference to the neat the chin rises upwards in front Jo escape beyond the arch, and thus the excavation. The three outline heads positions of the cranium after the chin has state of things from the foregoing obtains where of revolving towards the front, turns towards the back pelvis. Here the forehead must appear first; then the at the mouth; and lastly, the chin, escaping from the edge of ineum, retreats towards the point of the coccyx, allowing the it den of the head to pass out under the arch; and finally, the vertex or rehead born which concludes the delivery of the head. I say that the appears first, not that it is born first, for the part first is the chin. When the chin has escaped, and begun to retreat behind the perineum, the mouth becomes delivered, then the nose and eyes, top of the forehead, crown, and, lastly, the vertex. This must be the case, considering that the occipito-mental diameter is fully five inches long, and that there is no antero-posterior, oblique, or transverse in any part of the lower excavation. It is impos a diameter of ithin the ex he mental tal dia cape st. Fig. 83. FACE PRESENTATIONS, 879 which, in addition to a face presentation, there is a left foot. If, in such were thrust back e absence of a y bad case the sa d Fig. 79. vis, and the enormous or the exit of the child, in aat is produced by a rotation of the light, that I hope it may greatly assist dent how extremely important a matter it is aid and assistance to nature, in her attempts to ne front of the pelvis. of face presentations is not perfectly well understood; it wer, probable that they are more commonly occasioned by an quity of the womb than by any other cause. For example, let the womb, at the onset of labor, be so oblique as to throw its fundus far down to the left side, the child presenting by the head, and the vertex to the right side of the pelvis: the direction of the expulsive force operating on the infant will propel its head against the edge or brim of the pelvis, and either cause the head to glance upwards into the iliac fossa, so as to let a shoulder fall into the opening, or it will be turned over, so as to let the face fall into the opening, and thus produce a face presentation, in which the chin is near to the left acetabulum, and the forehead to the right sacro-iliac junction. It is easy to set this in a clear light, especially if it be accompanied with demonstrations on the phantome. In my opinion, it would be right to admit, in a systematic arrangement, only two original positions of face-presentations: viz., one with the chin to the right, and one with it to the left in the pelvis; it being always understood, that the position is not necessarily exactly trans throat can apply itself against the inside of the symphysis, allowing the chin, nay, the whole head to be born, before any part of the thorax of the infant begins to plunge into the excavation. Figure 81 may serve to show how the chin, in a favorable case, comes, at last, to the symphysis pubis, slides down behind it, and at length begins to emerge underneath the crown of the pubal arch. Look at the figure; reflect that the occipito-mental diameter is five inches, and the pelvis only four and a half; and that, as soon as the chin begins to come forward under the arch, the five inch mento-occipital diameter is coming, with its mental extremity, out beneath the arch. The next figure (Fig. 82) shows how the chin rises upwards in front of the pubis as soon as it begins to escape beyond the arch, and thus allows the head to roll out of the excavation. The three outline heads show the three successive positions of the cranium after the chin has once come under the arch. A very contrary state of things from the foregoing obtains where the chin, instead of revolving towards the front, turns towards the back part of the pelvis. Here the forehead must appear first; then the nose; next the mouth; and lastly, the chin, escaping from the edge of the perineum, retreats towards the point of the coccyx, allowing the crown of the head to pass out under the arch; and finally, the vertex emerges, which concludes the delivery of the head. I say that the forehead appears first, not that it is born first, for the part first born is the chin. When the chin has escaped, and begun to retreat behind the perineum, the mouth becomes delivered, then the nose and eyes, top of the forehead, crown, and, lastly, the vertex. This must be the case, considering that the occipito-mental diameter is fully five inches long, and that there is no antero-posterior, oblique, or transverse line of such length in any part of the lower excavation. It is impos sible then to see-saw a diameter of more than five inches within the excavation. Therefore, if the mental extremity of the occipito-mental diameter descends first, it must escape first, and the occipital extremity last. But, while the chin is sweeping, slowly and painfully, down the curve of the sacrum, and especially, when it is got so low as the edge of the perineum, the breast of the child is also entering the pelvis, where the space it should occupy is already taken up by the perpendicular diameter of the head. Imagine the Fig. 83. painful distension of the parts within the pelvis, and the enormous extension of the os externum, required for the exit of the child, in such a case! Figure 83 shows the difficulty that is produced by a rotation of the chin backwards, in so clear a light, that I hope it may greatly assist in teaching the young Student how extremely important a matter it is to give all possible aid and assistance to nature, in her attempts to turn it towards the front of the pelvis. The cause of face presentations is not perfectly well understood; it is, however, probable that they are more commonly occasioned by an obliquity of the womb than by any other cause. For example, let the womb, at the onset of labor, be so oblique as to throw its fundus far down to the left side, the child presenting by the head, and the vertex to the right side of the pelvis: the direction of the expulsive force operating on the infant will propel its head against the edge or brim of the pelvis, and either cause the head to glance upwards into the iliac fossa, so as to let a shoulder fall into the opening, or it will be turned over, so as to let the face fall into the opening, and thus produce a face presentation, in which the chin is near to the left acetabulum, and the forehead to the right sacro-iliac junction. It is easy to set this in a clear light, especially if it be accompanied with demonstrations on the phantome. In my opinion, it would be right to admit, in a systematic arrangement, only two original positions of face-presentations: viz., one with the chin to the right, and one with it to the left in the pelvis; it being always understood, that the position is not necessarily exactly trans verse, but that the chin may be variously addressed, sometimes, and indeed most generally being so far back as to be near the sacro-iliac symphysis, and sometimes more anteriorly, or near the body of the pubis; Velpeau prefers to have only two positions. By admitting these two positions only, the Student's mind is relieved from the burden of unnecessary artificial distinctions; and should he in practice rest upon them, it will be easier for him to comprehend the practical doctrines relative to the case. Thus, in all face cases, the great doctrine is to bring the chin to the pubic arch, because the chin, being the mental extremity of the five inch long mento-occipital diameter, may escape by gliding an inch downwards behind the symphysis pubis; whereas, if it be directed backwards to the sacrum, it must slide five inches down the sacrum and coccyx, and from three to three and a half inches over the extended perineum, before it can be born; but, five inches and three inches make eight inches. The child's neck is not eight inches long. Therefore, before the chin can slide down the sacrum, and off the anterior edge of the extended perineum, a good part of the child's thorax must be pressed or jammed into the excavation along with the head, the vertical diameter of which alone is more than three and a half inches. (See Figure 83.) If we should adopt four positions, we must have a doctrine for each; but with the two only, there is a necessity for only one doctrine-namely, to bring the chin to the arch of the pubis, if practicable; if not, let the forehead come, and do our best with it. Face presentations are accidents; and, perhaps, they are so unlikely to happen, in consequence of the normal law of foetal flexion, that they ought to be regarded as examples of preternatural labor. Yet, when we come to reflect that the female can generally expel the child with but little more difficulty, in this case, than in vertex positions, it seems altogether proper to regard them as natural cases. But I have said that they are accidents, and I believe that they are accidents caused by deviations of the axis of the womb. I beg leave to repeat that, if a female have a very great right lateral obliquity of the womb, and the vertex present towards the left side of the pelvis, it may be impelled against the brim in such a manner as to glance above it, and allow the forehead to fall into the opening, which state could not exist long without being followed either by the descent of the face, or the inducing of a shoulder presentation. It should never be forgotten that, from the chin to the vertex is a distance of five inches, which none of the diameters of the straits will take in, in the living subject: therefore, if the vertex should rise above the brim, and let the forehead fall into the opening, the chin would gradually come down. |