Licence: Public Domain Mark
Credit: Lectures on natural and difficult parturition / by Edward William Murphy. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![Vertica] Section of Pelvis, showing the anterior and posterior surface of the plane of the Ischium.—The lines represent the inclined plane of the promontory— plane of the brim—of the cavity—of the outlet. Vide p. 12. (in obstetric language) the plane of the ischium, because the bead of the child glides upon it in its descent, and passes forwards under the arch of the pubis; but if carefully examined, it will be found to consist of two planes very slightly inclined in opposite directions, and divided by a line passing from the pectineal emi- nence to the spine of the ischium. In some pelves, this is more obvious than in others; but when the soft parts are attached, this will be found nearly corresponding to the reflections of the peritoneum which form the broad ligaments. Thus, the inter- nal surface of the ischium before the soft parts are removed presents two broadly curved surfaces, one anterior, the other posterior; these greatly contribute to facilitate the rotation of the head of the child in passing through the pelvic cavity. The anterior plane terminates at the obturator foramen, an opening nearly filled with membrane, giving support to the internal and external obturator muscles, and offering less resistance to the advance of the head forwards, than if it consisted of bone. The obturator foramen is bounded by the ischio-pubic ramus, the pillar of the arch of the pubis. It presents a smooth surface, bevelled off towards the arch; and when the head passes from the obturator foramen upon it, this inclination greatly assists its exit under the arch of the pubis. The posterior plane terminates in the iscliiatic foramen, and the portion of the head which comes upon it, glides in a similar manner upon the coccygasus and](https://iiif.wellcomecollection.org/image/b21923334_0017.jp2/full/800%2C/0/default.jpg)
