. The science and art of midwifery. the hearts action in onefoetus counterbalances that of the other ; the stronger blood-current inthe placenta pushes back the weaker one, at first impeding the circula- * Ahlfeld, Beitrage zur Lehre von den Zwillingen, Arch. f. Gynaek., Bd. vii, MULTIPLE PREGNANCIES AND THEIR MANAGEMENT. 231 tion of the less favored foetus, then arresting it, and finally causing itto reverse its direction. The heart atrophies, and an acardia is pro-duced, which is simply an appendage to the healthy foetus. The cir-culation in the acardia takes place as follows : Venous
. The science and art of midwifery. the hearts action in onefoetus counterbalances that of the other ; the stronger blood-current inthe placenta pushes back the weaker one, at first impeding the circula- * Ahlfeld, Beitrage zur Lehre von den Zwillingen, Arch. f. Gynaek., Bd. vii, MULTIPLE PREGNANCIES AND THEIR MANAGEMENT. 231 tion of the less favored foetus, then arresting it, and finally causing itto reverse its direction. The heart atrophies, and an acardia is pro-duced, which is simply an appendage to the healthy foetus. The cir-culation in the acardia takes place as follows : Venous blood from thehealthy foetus is conveyed by the umbilical arteries to the placenta ;the force of the fetal heart drives the stream through the communi-cating branches to the umbilical arteries of the less favored twin ; thisforce is, however, insufficient to carry the current to the upper partsof the body, which are, therefore, not developed. The favorable posi-tion of the lower extremities for receiving the blood from the umbili-. Fio. 138.—Twin placenta, showing arterial anastomosis. cal vessels explains their continued though imperfect growth and de-velopment. The blood carried to the foetus by the umbilical arteriesis returned by the umbilical vein. According to Ahlfeld,* a division may take place in the formativematerial contained within a single area germinativa. This divisionmay be complete, and thus produce separate twins inclosed in thesame amnion, which not only are of the same sex, but bear to oneanother through life the most striking similarity as regards appear- * Ahlfeld, Die Entstehung der Doppelbildung und der bomologen Zwillinge, Arch,,f. Gynaek., Bd. ix, p. 196. 232 LABOR. ance, physical peculiarities, and both mental and moral characteris-tics ; or it may be incomplete, and thus give rise to conjoined twins,or one of the numerous forms of double monsters.*
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
