"It would be hard to conceive a system of instincts more nicely adjusted, where the constituents should represent or support one another better. The husband has an interest in protecting the wife, she in serving the husband. The weaker gains in authority and safety, the wilder and more unconcerned finds a help-mate at home to take thought of his daily necessities. Parents lend children their experience and a vicarious memory; children endow their parents with a vicarious immortality."