A treatise on the science and practice of midwifery . , its continuation. The os innominatum (Fig. 1) is an irregularly shaped bone origi-nally formed of three distinct portions, the ilium, the ischium, andthe pubes, which remain separated from each other up to and beyondthe period of puberty. They are united at the acetabulum by aY-shaped cartilaginous junction, which does not, as a rale, becomeossified until about the twentieth year. The consequence is that thepelvis, during the period of growth, is subject to the action of variousmechanical influences to a far greater extent than in adult l
A treatise on the science and practice of midwifery . , its continuation. The os innominatum (Fig. 1) is an irregularly shaped bone origi-nally formed of three distinct portions, the ilium, the ischium, andthe pubes, which remain separated from each other up to and beyondthe period of puberty. They are united at the acetabulum by aY-shaped cartilaginous junction, which does not, as a rale, becomeossified until about the twentieth year. The consequence is that thepelvis, during the period of growth, is subject to the action of variousmechanical influences to a far greater extent than in adult life; and3 26 ORGANS CONCERNED IN PARTURITION. these, as we shall presently see, have an important effect in deter-mining the form of the bones. The external surface and borders ofthe os innominatum are chiefly of obstetric interest from givingattachment to muscles, many of which have an important accessoryinfluence on parturition, such as the muscles forming the abdominalwall, which are attached to its crest, and those closing its outlet and Fig. Os InDominatuin. forming the perineum, which are attached to the tuberosity of theischium. On the anterior and posterior extremities of the crest ofthe ilium are two prominences (the anterior and posterior spinousprocesses) which are points from which certain measurements aresometimes taken. The internal surface of the upper fan-shapedportion of the os innominatum gives attachment to the iliacus muscle,and contributes to the support of the abdominal contents; along withits fellow of the opposite side it forms the false pelvis. The false isseparated from the true pelvis by the ilio-pectineal line, which, withthe upper margin of the sacrum, forms the brim of the pelvis. Thisis of especial obstetric importance, as it is the first part of the pelviccavity through which the child passes, and that in which osseousdeformities are most often met with. At one portion of the ilio-pectineal line, corresponding with the junction of the ilium a
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Keywords: ., bookcentury1800, bookdecade1870, bookidtre, booksubjectobstetrics
