A treatise on the science and practice of midwifery / By W. S. Playfair.
- William Smoult Playfair
- Date:
- 1885
Licence: Public Domain Mark
Credit: A treatise on the science and practice of midwifery / By W. S. Playfair. Source: Wellcome Collection.
Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.
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![Diameters as Altered by /^oft Parts.—In thinking of these measure- ments of the pelvis it must not be forgotten that they are taken in the dried bones, and that they are considerably modified during life by the soft parts. This is especially the case at the brim, where the projection of the psoas and iliacus muscles lessens the transverse diameter about half an inch, while the antero-posterior diameter of the brim and all the diameters of the cavity are lessened by a quarter of an inch. The right oblique diameter of the brim is, even in the dried pelvis, found to be on an average slightly longer than the left, jjrobably on account of the increased development of the right side of the pelvis from the greater use made of the right leg; but in addition to this the left oblique diam- eter is somewhat lessened during life by the presence of the rectum on the left side. The advantage gained by the comparatively frequent passage of the head through the pelvis in the right oblique diameter is thus explained. Other Measurements.—There are one or two other measurements of the true pelvis which are sometimes given, but which are of secondary importance. One of these, the sacro-cotyloid diameter, is that between the promontory of the sacrum and a point immediately above the coty- FiG. 9. Planes of the Pelvis with Horizon. A B. Horizon. c n. Vertical line. A B I. Angle of inclination of pelvis to horizon, equal to (10°. B I c. Angli; (if initliiiation of pelvis to spinal column, equal to 150°. C I J. .^nK!(• of hicliiiation of sacrum to spinal column, equal to 130°. E r. Axis of pelvic inlet. I, M. Mid plane in tlie middle line. N. Lowest point of mid plane of ischium. loid cavity, and averages from 3.4 to 3.5 inches. Another, called by Wood the lower or in(!lin(!d conjugate diameter, is that between the centre of the lower margin of the symj)]iysis pubis and the promontory](https://iiif.wellcomecollection.org/image/b2121072x_0051.jp2/full/800%2C/0/default.jpg)
