Mother, Nurse and Infant / A Manual Especially Adapted for the Guidance of Mothers and Monthly Nurses, Comprising Full Instruction in Regard To Pregnancy, Preparation for Child-birth, and the Care of Mother and Child, and Designed to Impart so Much Knowledge of Anatomy, Physiology, Midwifery, and the Proper Use of Medicines as Will Serve Intelligently to Direct the Wife, Mother and Nurse in All Emergencies.

by S. P. Sackett

Fig. 6. Vertical section of the pelvis.
Fig. 6—Inlet, outlet, and axis of the pelvis. a, b, plan of inlet—superior strait; c, d, plan of outlet, or inferior strait; e, f, axis of cavity; g, the coccyx extended as it is in labor.

Of the JOINTS OF THE PELVIS it is only necessary here to say that there is no motion in them to facilitate labor, except that the sacro-coccygeal joint is of the kind called ginglymoid, admitting of extensive motion, especially backward, so as to permit the enlargement of the lower outlet an inch or more. (Fig. [6].)

OF THE PELVIS IN GENERAL.

We will now consider the pelvis collectively or as a whole; its relation to the rest of the body; its magnitude, axis, etc. It is connected with the trunk by the articulation of the sacrum with the last lumber vertebra, effected in the same manner as the junction of the vertebra with each other; with the lower extremities it is connected by means of the hip joints. When the pelvis is in situ, the brim is neither horizontal nor perpendicular. It represents a cone, slightly flattened from before backwards, the base of which being above, while the apex is directed downwards.

When the body is erect the upper part of the sacrum and the acetabula are nearly on the same descending line, the point of the os coccygis being a little above the arch of the pubis, and the sacro-vertebral angle three inches and nine lines higher than the pubis. Were it not for the obliquity owing to the upright position of the human female, the womb would gravitate low in the pelvis, and produce most injurious pressure on the contained viscera. The lower or true pelvis is the part involved in parturition, and its size and shape demands our attention.

THE BRIM OF THE PELVIS.

This is defined by the LINEO ILIO PECTINEA, which marks the boundary of the true and false pelvis, and this superior strait is the entrance of the lesser pelvis. Its form has been variously described as being oval, heart-shaped, and triangular. If we call it “triangular with angles rounded off,” the base of the triangle is behind and the apex in front. It would be nearly oval were not the oval form broken by the promontory of the sacrum. This brim is the first solid resistance the head of the fœtus meets in its descent through the pelvis.

DIAMETER OF THE PELVIS.

Different estimates are made by different anatomists of the measurements of the brim of the pelvis. The following is nearly the correct size of the ordinary female pelvis: