. An American text-book of obstetrics. For practitioners and students. ity the irreg-ularities in the contour of the pelvic canal and the corresponding irregularitiesin the shape of the fetal head are matters of the greatest importance. It willbe remembered that although the transverse diameter of the superior strait isnominally the greatest, yet the rapid convergence of the ilio-pectineal lines asthey stretch forward renders the length of the practicable transverse diameterin fact less than that of the oblique diameters, so that any ovate body presentedto the inlet of the pelvis will tend to
. An American text-book of obstetrics. For practitioners and students. ity the irreg-ularities in the contour of the pelvic canal and the corresponding irregularitiesin the shape of the fetal head are matters of the greatest importance. It willbe remembered that although the transverse diameter of the superior strait isnominally the greatest, yet the rapid convergence of the ilio-pectineal lines asthey stretch forward renders the length of the practicable transverse diameterin fact less than that of the oblique diameters, so that any ovate body presentedto the inlet of the pelvis will tend to enter the brim in the oblique diameter. At the inferior strait the transverse diameter is the narrowest of the whole 398 A3IERICAN TEXT-BOOK OF OBSTETRICS. pelvis, and, since the oblique diameters at the moment of delivery are shorterthan the distended conjugate, any ovate body which attempts to pass the outletwill do so most readily if its long diameter corresponds with the antero-posteriordiameter of the inferior strait. It is therefore evident that the process of. Fig. 219.—Sagittal section of the pelvis, showing the pelvic axis and the curve of Cams. labor will most easily be accomplished by the occurrence of a rotation of thelongest diameter of the presenting parts from an oblique position at the supe-rior strait to an antero-posterior position at the outlet; in point of fact, themechanical relations which lead up to this rotation lie at the bottom of thewhole subject of the mechanism of labor. It is to be noted that when the woman is in the erect position the axis of thesuperior strait * forms an angle of about 30° with the horizon ; that in thesame position of the woman the axis of the inferior strait is directed down-ward and a little forward ; and that the axis of the vaginal outlet of the par-turient canal looks almost directly forward and but very slightly downward. Differences between the Male and the Female Pelvis.—It is importantthat the obstetrician should c
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectobstetrics, bookyear1
