Licence: Public Domain Mark
Credit: Practical manual of obstetrics. Source: Wellcome Collection.
Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.
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![ward and backward from the navel. The study of these dimensions is of the utmost importance, the first to be considered being— 1. The anteroposterior or sacro-pubic diameter runs from the sacro- vertebral angle to the summit of the symphysis pubis. It is 11 ctm. (4£ in.) on the average, but, because of the projection from the posterior surface of the symphysis pubis, we can only consider the smallest sacro- pubic diameter, called the working diameter (diametre utile), which varies from 9£ to 10i ctm. (3 to 4 in.). 2. The two oblique diameters pass from the ilio-pectineal eminence of one side to the sacro-iliac synchondrosis of the other. The left oblique is the one commencing at the ilio-pectineal eminence of the left side. [The majority of standard text-books in the English language designate the left oblique diameter as that starting from the left sacro-iliac synchondrosis, the right oblique diameter commencing at the right synchondrosis.—Ed.] Both obliques measure 10 ctm. (3.9 in.). 3. The transverse diameter runs from the centre of the lower border of the iliac fossa of one side to a corresponding point on the other. It is 134 ctm. long (5 in.). 4. The two sacro-cotyloid lines are measured from the sacro-vertebral angle to the posterior portion of the acetabulum on each side. They are 9 ctm. long (3^ in.). The circumference of the superior strait or innomi- nate line measures, on the average, 40 ctm. (15f in.). § 4. The Inferior Strait.—The inferior strait has a very irregular contour, but tracing it on a sheet of paper on which the pelvis is placed, it shows a more regular oval form, with the longest diameter antero-posterior- ly. It presents three bony projections: the coccyx behind and the tuber is- chii of each side, separated by three large notches, viz. : the pubic arch in front and the two sciatic notches at the Sides the ^OOOfX-paUoi^ right and leftObUqoe; 8, bNUMVWMOC bi-Uehiutk-. latter rendered shallower by the presence of the sacro-sciatic ligaments. The plane of the inferior strait has a slight obliquity, fche inclination running downward and backward. In the upright position it forms an angle of 11° with the horizon, bat during delivery the retrocession of the coccyx nearly etVaces this Uigk : indeed, the direction of all these planes varies with the changing attitude of the individual. The axis of the inferior strait is a line drawn from the sacro-vertebral](https://iiif.wellcomecollection.org/image/b2100013x_0041.jp2/full/800%2C/0/default.jpg)
