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XXII.— On the Laws of the Fertility of Women. By J. Matthews Duncan, M.D. 



(Bead 6th February 1866.) 



In a former paper* I described the variation of the fecundity of women 

 according to age, and arrived at the conclusion that the climax of fecundity in 

 women was at or near the age of 25 years. Researches, completed since that 

 paper was read, regarding the variations of length and weight of children accord- 

 ing to the mother's age, and regarding the mortality of childbed as influenced by 

 the mother's age, have been published in the " Edinburgh Medical Journal." The 

 results of these investigations seem to illustrate and confirm the statement made 

 as to the age of the climax of fecundity, for I have found that, about that age, women 

 produce the bulkiest children, as measured by length and weight ; and about the 

 same age of the mother there is the smallest mortality in childbed. As still 

 further adorning the age of 25, I may add, that several sets of observations, 

 including some made in St George's-in-the-East, London, and published in the 

 eleventh volume of the "Journal of the Statistical Society," show a greater amount 

 of survival and rearing among children born of women about that age than at any 

 other ; and recently Dr Arthur Mitchell has published a collection of cases of 

 idiocy, with the respective ages of the mothers at the time of the idiots' births, 

 and these also show a smaller proportion born of women about the age of 25 

 years than at greater and lesser ages.f 



In the last portion of the paper first alluded to, having described initial fecun- 

 dity, the age at which women are most likely to beget children soon after marriage, 

 I said that I could not advance further without encroaching on another topic, viz., 

 the fertility of marriage ; or, as marriage is scarcely admissible as a term in phy- 

 siology, the subject may be designated " sustained fecundity," or the laws of the 

 fertility of women cohabiting with men during the child-bearing period of life. 

 It is this subject which I propose here to enter upon. So far as I know, very 

 little is ascertained or known in this department of physiology. The writings upon 

 it are for the most part to be found in the works of political economists, and are 

 chiefly confined to the single question of the rate of increase of a population under 

 varying circumstances. To illustrate this topic, which is one of little interest to 

 the physiologist, data are numerous and abundant. But when the writers re- 

 ferred to attempt to go deeper into the fundamental laws of the fertility of 

 women, having very scanty materials and using them without care, they arrive at 

 scanty results, which are either positively erroneous or of little value. 



* Trans. Roy. Soc. of Edinburgh, vol. xxiii. p. 475, &c. 

 •J 1 Edinburgh Medical Journal, January 1866. 



VOL. XXIV. PART II. 4 I 



