Obstetrics : a manual for students and practitioners / by W.P. Manton.

  • Manton, W. P. (Walter Porter), 1858-1925.
Date:
[1905]
Catalogue details

Licence: In copyright

Credit: Obstetrics : a manual for students and practitioners / by W.P. Manton. Source: Wellcome Collection.

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    nata, which are firmly bound together by ligaments. It is divided by the iliopectineal line into two portions—an upper or false pelvis, and a lower or true pelvis. The latter only is of special interest. The upper opening of the true pelvis is somewhat cordate in form, and is called the superior strait, margin, isthmus, inlet, or brim. The lower opening is more oval, and is called the inferior strait or outlet. The space between the brim and the outlet is the cavity. The Planes of the Pelvis. The pelvic canal is short and curved, and varies somewhat in shape in its different parts. In order to understand these varia- tions more exactly, for purposes of measurement, etc., imaginary surfaces, called planes, are taken transversely through the canal at different levels. The lines of these surfaces are not parallel, but converge from behind forward, so that if they were carried out, would unite about 1£ inches in front of the symphysis pubis. The planes of the pelvis are not to be confused with the anterior and posterior inclined planes of the cavity, which are formed by the sloping walls of the ischium in front and the ischial spines behind. Three planes are of importance—that of the brim, the cavity, and the outlet. Plane of the Brim.—From the summit of the sacral promon- tory, iliopectineal line, and posterior surface of the symphysis pubis, -J of an inch below its upper margin. It forms an angle with the horizon of about 50° or 60°. Plane of the Cavity.—From the upper end of the third sacral vertebra, centre of acetabulum, and middle of the posterior sur- face of the symphysis pubis. Plane of the Outlet.—From the end of the sacrum, ischial tuberosities, and posterior surface of the symphysis pubis just above its lower margin. A line drawn from the tip of the coccyx to the subpubic margin, representing the anatomical outlet, forms an angle of 10° with the horizon. On account of the yielding structures at the anatomical outlet the plane of the obstetric outlet is taken from the most resisting points. As the birth-canal is curved it is necessary to determine its axis in order to understand the direction in which the foetal head travels in its descent through the pelvis.
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