. The science and art of midwifery. Diameters of the outlet. The circumference icus (vide Fig. 98).sixteen inches. The inferior strait proper, or outlet of the pelvis, is bounded bythe sub-pubic ligament, the pubic rami, the rami and tuberosities ofthe ischia, the sciatic ligaments, and the coccyx. Owing to the pro- MECHANISM OF LABOR. 159 jection of the iscliia, the surface of the pelvic outlet is rendered con-vex, or, perhaps, is better described by supposing it to be composedof two obtuse-angled triangles with apices at the symphysis and coccyx,and with a common base formed by a line drawn
. The science and art of midwifery. Diameters of the outlet. The circumference icus (vide Fig. 98).sixteen inches. The inferior strait proper, or outlet of the pelvis, is bounded bythe sub-pubic ligament, the pubic rami, the rami and tuberosities ofthe ischia, the sciatic ligaments, and the coccyx. Owing to the pro- MECHANISM OF LABOR. 159 jection of the iscliia, the surface of the pelvic outlet is rendered con-vex, or, perhaps, is better described by supposing it to be composedof two obtuse-angled triangles with apices at the symphysis and coccyx,and with a common base formed by a line drawn through the ischia. The antero-posterior diameter extends from the lower border ofthe symphysis to the extremity of the coccyx. It measures three andthree quarters inches, though, when the coccyx is pushed backward,the distance may be extended to four and a half inches. The transverse diameter, between the inner borders of the tuberos-ities, measures four and a quarter inches. COCCYX PUSHED BACK. OBSTETRICAL CONJUGATE, HORIZON. PLANEOF OUTLET Fig. 98.—Section showing the inclination of the pelvis according to Naegele. (Tarnier et Chantreuif.) Owing to the elasticity of the sciatic ligaments, the oblique diam-eters are not regarded as of obstetrical importance. The axis of the inferior strait, when the coccyx is not disturbed,strikes the promontory. When the coccyx is pushed backward, a per-pendicular line drawn from the center impinges upon the lower bor-der of the first sacral vertebra. The circumference of the inferior strait measures thirteen and ahalf inches. The pelvic cavity or canal possesses an irregular, cylindrical shape,constricted somewhat above at the superior strait, and narrowing rap-idly at the pelvic outlet. Below the brim, the dimensions are in-creased considerably by the concavity of the sacrum. Thus, a planepassing through the lower portion of the symphysis pubis, and across 100 LABOR. the upper margins of the acetabula, to the junction of the second andt
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
