A system of obstetrics . haltnisses bei der Vennehrung der Menschen,Thiere, u. Pflanzen, Jena, 1884. 2 According to Diising (loc. cit.), women impregnated in summer give birth to fewerboys than those impregnated in winter (conclusions based on more than ten and a halfmillion births). 3 Ploss found in Saxony that up to 2000 feet the greater the altitude the larger wasthe number of male births (at 2000 ft., ). 4 Darwins Collected Works. 5 Conclusion of Veit, based on more than thirteen million births. 6 Ahlfeld: Arch, f. Gyn., Bd. ix. S. 196. 7 Occasionally two foetuses are found in a s
A system of obstetrics . haltnisses bei der Vennehrung der Menschen,Thiere, u. Pflanzen, Jena, 1884. 2 According to Diising (loc. cit.), women impregnated in summer give birth to fewerboys than those impregnated in winter (conclusions based on more than ten and a halfmillion births). 3 Ploss found in Saxony that up to 2000 feet the greater the altitude the larger wasthe number of male births (at 2000 ft., ). 4 Darwins Collected Works. 5 Conclusion of Veit, based on more than thirteen million births. 6 Ahlfeld: Arch, f. Gyn., Bd. ix. S. 196. 7 Occasionally two foetuses are found in a single amniotic cavity, which is to be THE MATURE FCETUS. 219 of the foetuses will be the same. The placentae will usually be foundintimately united when expelled at term, presenting extensive arterialand venous anastomoses—a condition that may give rise to the deform-ity of one of the twins known as acardia (see p. 300, this section). Butid the early stages of development each placenta, even in unioval twins, Fig. Twin Placenta, showing extensive anastomosis of the blood-vessels. is separate When the embryos are derived each from a separate ovum,there should be separate decidual reflexa?, chorions, and placentae. Occa-sionally, however, when the ova are implanted close together, the pla-centae may join one another, there may be but one decidua reflexa, andit may be difficult to detect the double layer of chorion that shouldseparate the two ova. Although twins are not infrequently born, the condition should beregarded as pathological in its influence, at least, upon the statistics collected by Sehatz,1 it appears that in twins from dif-ferent ova one would be born dead in every 23 cases, while from thesame ovum the death-rate would be 1 : 6*. One foetus will perhaps explained (1) by the atrophy arid absorption of the contiguous amniotic walls; (2) byrupture of the amnion in the later months from the vigorous movements of the foetus;or (3) by the development o
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
