The practice of obstetrics, designed for the use of students and practitioners of medicine . ions are in completing the birth of the child inbreech cases, when the after-coming head has passed below the retracted fundus. (2) The Vagina and Pelvic Muscles.—At term the musculature of the vaginais hypertrophied to a considerable extent and is important in the expulsion ofparts of the ovum that can be acted on by peristalsis. The period when its actionis most valuable is during the expulsion of the placenta. The only pelvic mus-cles of the pelvic floor concerned in expulsion are the levator ani, t
The practice of obstetrics, designed for the use of students and practitioners of medicine . ions are in completing the birth of the child inbreech cases, when the after-coming head has passed below the retracted fundus. (2) The Vagina and Pelvic Muscles.—At term the musculature of the vaginais hypertrophied to a considerable extent and is important in the expulsion ofparts of the ovum that can be acted on by peristalsis. The period when its actionis most valuable is during the expulsion of the placenta. The only pelvic mus-cles of the pelvic floor concerned in expulsion are the levator ani, the transversi,the sphincters of the vagina and of the anus. Their action is imperfectly peri-staltic and assists the muscle of the vagina. 2. The Involuntary Forces, or Uterine Contractions.—The uterus, during the * It was at one time held that the abdominal wall was the sole cause of the birth ofthe child; later it was taught that it played no part, but Schroeder showed that both uterineand abdominal contractions were concemed in the expulsion of the fetus. THE EXPELLING FORCES. 429. Fig. 553.—Shape of the Uterus during thePeriod of Relaxation. contractions of the second stage, is retained in its position by means of the roundligaments, which are composed chiefly of involuntary muscle-fibers, assisted bythe muscular part of the broad ligaments. In contracting, the round ligamentstend to force the fundus downward and forward, and by their action on theupper part of the uterus they are one factor in the increase of intrauterinepressure. After the uterus has been raised by the round ligaments, however,abdominal pressure can act to betteradvantage. (i) Involuntary. — Although theuterine contractions have no depend-ence on the will,—i. e., they are in-voluntary,—they may be consider-ably influenced by the brain, as maybe seen by the effect of mental emo-tions. (2) Peristaltic.—Like other organscomposed of non-striated muscle, thecontractions are assumed to be peris-ta
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectobstetrics, bookyear1
