This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1850 edition. Excerpt: ...this rule may not hold good in many single fami ies that may be noticed, but it will always do so when the average is taken of a large number, and the chances are of course in the same ratio in every instance. Thus in every case when the father is over eighteen years older than the mother it is two chances to one that the child will be a boy, and in three hundred such births there would be just two hundred male to one hundred females; while if the mother be so much the elder the chances and results will be just the same the other way. The relative age, therefore, has a most potent influence over the sexual formation, but still there are evidently other agencies also, because it does not operate in every individual case, and we must therefore endeavor to discover what those other agencies are. My own impression is that in the exceptional cases, where the elder parent does not impart the sex, it is owing to the younger parent being much the more vigorous. This view I have ad many opportunities of verifying, in confidential communications, and I have almost invariably found it correct. This also shows why it is that the greater age is no advantage beyond a certain period. Thus for instance if the father be overfifty, while the mother is under thirty-five, the rule will change, and the number of girls will predominate. We also find that the greater number of first children are boys, especially if born soon after marriage, owing to the father being naturally most powerful then. In illegitimate children on the contrary there are most girls. probably because in many of these cases the female is more vigorous than ordinary.--In those countries where polygamy predominates, or where, the men have several wives, there are many more girls born than...