The principles and practice of obstetrics . arious parts, which is demonstration itself that the order is duealtogether to the movement of extension, which the head is gradu-ally undergoing, at this stage of the labor, during its passage intothe world. Thus, the result of extension is to afford egress suc-cessively, through the antero-posterior or cocci-pubic diameter, tothe perpendicular, occipito-frontal, and occipito-mental diametersof the head. It is at this period of the parturient effort that theperineum undergoes its maximum distension, so that the axis ofthe inferior strait is elongate
The principles and practice of obstetrics . arious parts, which is demonstration itself that the order is duealtogether to the movement of extension, which the head is gradu-ally undergoing, at this stage of the labor, during its passage intothe world. Thus, the result of extension is to afford egress suc-cessively, through the antero-posterior or cocci-pubic diameter, tothe perpendicular, occipito-frontal, and occipito-mental diametersof the head. It is at this period of the parturient effort that theperineum undergoes its maximum distension, so that the axis ofthe inferior strait is elongated forward and upward. The moment,however, the head has completely freed itself from the os externum,the anterior border of the perineum recedes, and comes directlyin contact with the front of the childs neck. The immediate con-sequence of this recession of the perineum is to cause the head,which had previously been elevated toward the pubes, to fall byits own gravity downward toward the coccyx. THE PRINCIPLES AND PRACTICE OF OBSTETRICS. 51. External Rotation.—The head is liberated—it has made itsescape through the vulva, and now let us trace its further it first passes into the world—in this left occipito-acetabularposition—it is, as you have seen, so situated that the occiput is incorrespondence with the symphysis pubis, while the face is down-ward regarding the coccyx. Almost immediately, however, afterits escape, it undergoesanother change of posi-tion, which results inplacing the occiput to-ward the left groin(Fig. 27), and the facein the direction of theopposite ramus of theischium. Until thepublication of the paperof M. Gerdy, this fifthmovement of the headwas described as themovement of restitu-tion, and the followingwas the explanationgiven by Baudelocque,who, I think, was the first to direct attention to it—he supposed that when the headrotated in the pelvic cavity, it did so at the expense of the bodyof the child—in other words, the body did
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Keywords: ., bookcentury1800, bookdecade1860, bookpubli, booksubjectobstetrics
