File:The principles and practice of obstetrics (1864) (14596437320).jpg

Identifier: 67240830R.nlm.nih.gov
Title: The principles and practice of obstetrics
Year: 1864 (1860s)
Authors: Hodge, Hugh L. (Hugh Lenox), 1796-1873
Subjects: Obstetrics Obstetric Surgical Procedures Pregnancy
Publisher: Philadelphia : Blanchard and Lea
Contributing Library: U.S. National Library of Medicine
Digitizing Sponsor: Open Knowledge Commons, U.S. National Library of Medicine

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small, thatrotation may occur, so as to get the sagittal suturebehind the pubis, the os frontis to the perineum, andthe chin toward the hollow of the sacrum, where thearrest of the head will again occur. Such a case theauthor has not met with. In the second position of a frontal presentation—adeviation from the second of the vertex—the mechanismdoes not differ from the former, or first position, ex-cepting in the fact that the head is oblique, betweenthe right acetabulum and the left sacro-iliac symphysis.Hence, in this case, the parieto-mental diameter corre-sponds to the right oblique, the bi-temporal or bi-pa-rietal to the left oblique, and the cervico-frontalcorresponds to the axis of the superior strait. Ofcourse this necessitates the left parietal boss to beopposed to the left acetabulum, and the right to theleft sacro-iliac symphysis. The head, therefore, if notconverted into a face presentation, will be aneither at the floor of the pelvis without rotation having Plate XXIV
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T Sinclairs lift. PWa TREATMENT. 23 occurred, or at the inferior strait after rotation hasbeen effected, bringing the chin toward the hollow ofthe sacrum. The third position of an os frontis presentation—adeviation from the third of the vertex—may be alludedto in this systematic arrangement, but in practice itcan hardly exist, after expulsive contractions have com-menced. The sharp point of the chin will almost in-evitably be turned off from the promontory of thesacrum, so as to give an oblique position to the head;or else it will so readily glide under the promontory ofthe sacrum as to insure a speedy conversion into a facepresentation. The fourth position of a frontal presentation—a de-viation from the fourth of the vertex—is, of course, thereverse of the first position. In this case, therefore,the chin will be toward the left acetabulum, the middleof the parietal bones toward the right sacro-iliac sym-physis, the left parietal protuberance over the rightacetabulum, and the

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