Note 238-2 — Chapter I

The researches of modern physiology make it probable that an ovum is detached from the ovaries at each period of healthy menstruation. (Bischoff, Beweis der von der Begattung unabhängigen periodischen Reifung und Lösung der Eier bei den Säugethieren und Menschen, 1844.) It is hardly possible to ascertain how many of these ova are capable of fecundation. Among the animals, on which the greater number of accurate observations have been made, that is in the case of horses, it has been found that, in the two districts of Prussia most favorably conditioned, of 100 mares that had been lined, 63.3 became pregnant, and 53.5 gave birth to live foals; in the rest of the Prussian monarchy, the births were only 46 per cent. Compare Schubert, Staatskunde, VII, 1, 98. In the Belgian haras (places for breeding horses), between 1841 and 1850, about 30 per cent. of the "leaps" proved fruitful, from 2 to 3 per cent. aborted, the rest were either probably or certainly unfruitful. (Horn., Statist. Gemälde, 171.) In the human species, also, the great number of first-born generated in the first weeks of marriage, bears witness to a high degree of procreative susceptibility.

On the other hand, the healthy male semen ejected during a single act of coition contains innumerable germs, a very few of which are sufficient to produce fecundation. (Leuckart, loc. cit, 907.) According to Oesterlen, Handbuch der medicischen Statistik, 1865, 196, from 10 to 20 per cent. of all marriages were childless. In the United Kingdom, Farr, report on the Census of 1851, estimated that in a population of 27,511,000, there were 1,000,000 childless families, when the term is allowed to embrace widows and widowers as well as married couples.