In various parts of Europe, according to Prof. Faye and other authors, “a still greater preponderance of males would be met with, if death struck both sexes in equal proportion in the womb and during birth. But the fact is, that for every 100 still-born females, we have in several countries from 134.6 to 144.9 still-born males.” Moreover during the first four or five years of life more male children die than females; “for example in England, during the first year, 126 boys die for every 100 girls,—a proportion which in France is still more unfavourable.”[371] As a consequence of this excess in the death-rate of male children, and of the exposure of men when adult to various dangers, and of their tendency to emigrate, the females in all old-settled countries, where statistical records have been kept,[372] are found to preponderate considerably over the males. It has often been supposed that the relative ages of the parents determine the sex of the offspring; and Prof. Leuckart[373] has advanced what he considers sufficient evidence, with respect to man and certain domesticated animals, to shew that this is one important factor in the result. So again the period of impregnation has been thought to be the efficient cause; but recent observations discountenance this belief. Again, with mankind polygamy has been supposed to lead to the birth of a greater proportion of female infants; but Dr. J. Campbell[374] carefully attended to this subject in the harems of Siam, and he concludes that the proportion of male to female births is the same as from monogamous unions. Hardly any animal has been rendered so highly polygamous as our English race-horses, and we shall immediately see that their male and female offspring are almost exactly equal in number.