A System of midwifery : including the diseases of pregnancy and the puerperal state . entredraw an infinite number of radii ] ass-ing through the pelvic cavity : eachof these radii may be held to representthe plane of that portion of the cavitythrough which it passes. If Ave thendraw a line which shall pass throughthe geometrical centre of each of theseplanes, that line will be found to bo acurve, which coincides very closelywith the axis of the true pelvis, whichis the segment of no circle, and whichhas been described as an irregular para-bola, (hie point must here, however,be noted—that as t
A System of midwifery : including the diseases of pregnancy and the puerperal state . entredraw an infinite number of radii ] ass-ing through the pelvic cavity : eachof these radii may be held to representthe plane of that portion of the cavitythrough which it passes. If Ave thendraw a line which shall pass throughthe geometrical centre of each of theseplanes, that line will be found to bo acurve, which coincides very closelywith the axis of the true pelvis, whichis the segment of no circle, and whichhas been described as an irregular para-bola, (hie point must here, however,be noted—that as the terminal planesor radii will he modified by the motionof the coccyx during labor, so in likemanner will the inferior portion of thecurve be proportionally altered. Thisis indicated in the diagram, where theline cf marks the parabolic curve orassumed true pelvic axis. We must here be careful in drawinga distinction between the axis of theoutlet of the bony pelvis, and that axis which represents the directionin which the child is horn. In considering the latter, it is essential. Diagram showing the axis of theparturient canal. II.] INTERIOR OF PELVIS. 43 that the soft part- forming the floor of the pelvis should he looked uponas constituting the posterior and inferior boundary of a continuationof the pelvic canal. These parts, which extend from the tip of thecoccyx to the posterior commissure of the vagina, are subjected duringdelivery to an amount of stretching for which nature makes due pro-vision. The sphincter of the ami _ed asunder, the perineumads in all directions in a manner apparently incompatible with the_ -ity of that structure, until ultimately, at the moment of expul -the fourchette is driven downwards ami carried forwards to such anextent, that a line drawn from the subpubic angle to the edge of the tded perineum, shows the plane of the outlet of the cpelvic canal t look, not downwards, hut almost directly forwards \ perpendicular t. and meeting the centre of t
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectobstetrics, bookyear1
