The causation of sex : a new theory of sex based on clinical materials ; together with chapters on the sex of the unborn child, and on the determination of sex at will / by E. Rumley Dawson.

  • Dawson, E. Rumley (Ernest Rumley), -1918.
Date:
1909
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The causation of sex : a new theory of sex based on clinical materials ; together with chapters on the sex of the unborn child, and on the determination of sex at will / by E. Rumley Dawson. Source: Wellcome Collection.

    156/250 (page 138)
    138 THE CAUSATION OF SEX fact Schroeder pointed out long ago), but often joined together. Play fair (p. i86) says : Conjoined twins must of necessity arise from a single ovule with a double germ, and there is no instance on record in which they were of opposite sexes. This should, I think, help to prove my theory, by showing that one ovary always breeds true^ That is, ova from one ovary only produce one sex. The children's hair will always be the same colour when derived from a single ovum, whether the twins are conjoined or not. Undoubted examples of ova with double germs or two nuclei have been reported by several observers. Norris and Dickinson ^ reproduce a drawing of Von Herff^s showing two well-marked nuclei in one ovum, and Whitridge Williams ^ figures a good example, the two germinal vesicles or nuclei being distinctly separated in the ovum ; while he states that the existence of such ova (containing two distinct germinal vesicles) is indisputable. Dr. T. Wilson ^ says : There is a much greater predisposition to the occurrence of hydramnion in cases of twins derived from a single ovum than in the commoner variety of twins developed from separate ova. The unioval variety of twins is of interest for many reasons. The foetuses are always of the same sex, and are much more alike than are those developed from different ova. They have a single placenta, in which an anastomosis takes place between their vessels ; acardiac monsters are generally admitted to arise only in this variety of pregnancy. Some cases of twins from a single ovum—possibly all the acardiacs—are believed to arise, not from double nuclei in an ovum, but by splitting or division into two of a single nucleus, though no one has seen such an occurrence ; but single nuclei have been seen to contain two nucleoli or germinal spots, as in a specimen figured by Nagel in Play fair s Midwifery ; so it is possible that, division of the nucleus being merely supposition, it is not necessary, if it occur at all. It must not be supposed, if two G. Fs. rupture, and two ova are discharged, that they are sure both to be fertilised ; ' Norris and Dickinson, American Text-book of Obstetrics, 1897, p. 71. W. Williams, op, cit., p. 327. ' Trans. Obstet. Soc., 1899, p. 237.