. Obstetrics: the science and the art. re-sisting perineum and posterior vaginal wall. These efforts, beingoften repeated, serve to push the perineum away from the croAvn ofthe pubal arch to let the vertex escape under it; but, while the peri-neum is being pushed off by this force, the same perineum jams the MECHANICAL INFLUENCE OF THE PELVIS. iO Fig. 21. occipital bone of the child firmly against the crown of the arch; sothat, as the vertex emerges from the genital orifice, the os occipitisis pressed, as I said, close to the symphysis, first at its lower edge,and next on its oater or front as
. Obstetrics: the science and the art. re-sisting perineum and posterior vaginal wall. These efforts, beingoften repeated, serve to push the perineum away from the croAvn ofthe pubal arch to let the vertex escape under it; but, while the peri-neum is being pushed off by this force, the same perineum jams the MECHANICAL INFLUENCE OF THE PELVIS. iO Fig. 21. occipital bone of the child firmly against the crown of the arch; sothat, as the vertex emerges from the genital orifice, the os occipitisis pressed, as I said, close to the symphysis, first at its lower edge,and next on its oater or front cranium of the child is born as soonas the extension is complete, but notuntil then. 99. Figure 21- exhibits the manner inwhich the vertex touches the inner sur-face of the crown of the arch when therotation is complete. The faint linesshow how it rolls out under the edge ofthe triangular ligament, and also how itnext rises upwards in front of the outersurface of the symphysis, the head turn-ing over backwards as it 100. Restitution.—As soon as the head is born, it begins torotate back again, outside of the pelvis, to the same point or direc-tion it had upon first engaging within the pelvis. Its originallyoblique position becomes restored, and this, which is the last act ofthe mechanism, as to the head, is called the restitution, whichdepends on the mechanism of the shoulder delivery. 101. Mechanism of the Shoulders Delivery.—The cause ofrestitution is to be sought for in the state or position of the the vertex is at the left acetabulum, the rio-ht shoulder is atthe right acetabulum, and the left one at the left sacro-iliac synchon-drosis : but the inclined plane of the right ischium repels the de-scending right shoulder, pushing or sliding it downwards, forwards,and to the left, until it comes to the symphysis pubis. The leftshoulder meanwhile falls into the open chasm of the hollow of thesacrum that yawns to receive it freely, 102. This
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectobstetrics, bookyear1
