On the alleged infecundity of females born co-twins with males : with some notes on the average proportion of marriages without issue in general society / by James Y. Simpson.

  • Simpson, James Young, 1811-1870.
Date:
[©1844?]
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Licence: Public Domain Mark

Credit: On the alleged infecundity of females born co-twins with males : with some notes on the average proportion of marriages without issue in general society / by James Y. Simpson. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    to twins among goats, not having access in this district of country to any information or direct observation upon the subject in that animal. I have hitherto been equally unsuccessful in tracing out any instance of a twin mare or she-ass, born under the circumstance already pointed out, being reared to maturity. The mare, in- deed, appears only in extremely rare cases to produce twins, and these twins are almost always endowed with such feeble powers of life as seldom to survive for any length of time after birth. Sir Everard Home, in a paper On Animals preternaturally formed at the time of birth, inserted in the Philosophical Trans- actions for 1799, and in the third volume of his Comparative Ana- tomy, after assuming that certain sexual organs in the male and female are originally identical or neuter in their character, and are only afterwards changed to the male or female type according to ulterior circumstances, adds the following observations :— If it is allowed that the sex is impressed upon the ovum at the time of impregnation, it may, in some measure, account for the free-mar- tins occurring when two young are to be impressed with different sexes at one impregnation, which must be a less simple operation, and, therefore, more liable to a partial failure than when two or any greater number of ova arc impressed with the same sex. It may also account, he remarks in reference to the human subject, for twins being most commonly of the same sex; and when they are of different sexes, it leads us to inquire whether the female, when grown up, has not, in some instances, less of the true female character than other women, and is not incapable of hav- ing children. In warm countries, Sir Everard adds, nurses and midwives have a prejudice that such twins seldom breed.* In reference to this last remark it is not unimportant to observe, that, as I have repeatedly found during the course of my inquiries upon this subject, a similar prejudice in reference to the inl'ecun- dity of human females born co-twins with males, exists to a con- siderable extent among the peasantry of the Lothians, and has very probably been derived from the analogy of the free-martin cow. The mischief, justly observes a late physiological author, to which the o])inion might give rise in causing a girl to be rejected as a wife for a defect, or taken for an excellence, (according as sterility might be regarded,) which she did not possess, is incalcu- lable.f The truth or falsity of the opinion itself can only be satisfac- torily settled by an appeal to a sufficient number of accurately as- certained histories of cases in wiiich women, born co-twins with males, have reached an adult age and become married. I have collected what may probably be considered as a suffi- * Comparative Anatomy, Vol. iii. pp. 333-4. f See foot-note at page 74 of Dr Fletcher's Rudiments of Physiology.