A manual of practical obstetrics . tip of the coccyx to the highestpoint of the pubic arch will meet the horizon at an angle ofabout 11°, which, however, is subject to variation, inasmuchas the pressing back of the coccyx during labor also presses itstip downward to some extent, which, of course, renders theangle more acute. The axis of the plane of the inferior straitnearly agrees with a line drawn from the sacral promontoryto the anterior verge of the anus. v The axes of the planes of the pelvic cavity are lines drawnthrough the centres of the planes at right angles to their sur-face. The ax
A manual of practical obstetrics . tip of the coccyx to the highestpoint of the pubic arch will meet the horizon at an angle ofabout 11°, which, however, is subject to variation, inasmuchas the pressing back of the coccyx during labor also presses itstip downward to some extent, which, of course, renders theangle more acute. The axis of the plane of the inferior straitnearly agrees with a line drawn from the sacral promontoryto the anterior verge of the anus. v The axes of the planes of the pelvic cavity are lines drawnthrough the centres of the planes at right angles to their sur-face. The axes of a great number of such planes, placed endto end, would form an imperfectly circular curve, or at least PLANES OF THE PELVIS, 33 a polyhedral arc of a curve, which would represent the realaxis of the pelvic canal. Such a curve was described by Carus,and known as Caruss curve, by placing one leg of a pair ofcompasses on the middle of the posterior edge of the sym-physis pubis ^in a bisected pelvis), the other leg of the corn-. Axis of the pelvic canal. pass having its point placed midway between the pubis andsacrum, and being moved so as to describe a curve from thesuperior to the inferior strait. But the true axis of the pelviccanal is not so geometrically perfect an arc of a circle as to 34 THE PELVIS. admit of being drawn in this manner; it is more nearly thecurve of an irregular parabola. (See Fig. 3, page 33.) The pelvic canal in the living female does not really ter-minate at the inferior strait. In so far as its osseous walls areconcerned it does, but the muscles and soft parts below forma continuation of the canal, and when these are stretchedduring parturition the posterior wall of the lower, muscularpart of the canal, viz., from the coccyx to the mouth of thevagina, measures quite as much as does the upper bony part,viz., from the coccyx to the sacral promontory. The anteriorwall of the muscular part of the passage, corresponding withthe pubis of the bony part, i
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherphila, bookyear1895
