In the middle classes the circumstances and duties of a woman’s life are entirely different. After marriage, a limited income and maternal and domestic duties limit a woman’s social education, and if her mental powers have not been fully developed by education it is difficult for her to resist the tendency to become absorbed in her purely personal worries and cares; brain atrophy sets in, and with it old age, the closing up of the mental avenues to new impressions and feelings. Thus any child at a Board school can be taught arithmetic, and most children at a high school can make progress in geometry and algebra, but even capable middle class women, who begin these subjects for the first time in early middle life, are frequently found to be mentally incapable of the reasoning processes involved. In one hundred years the age of childish irresponsibility has been raised from six to about twelve, and in the extra six years thus granted imagination and individuality have been left free to develop themselves. During the last twenty years another change has taken place. The duties of the young person have altered. Formerly at the age of eighteen, in the young person’s fiction, she was expected to relieve her invalid mother of household cares and brighten her aged father’s declining years. But mothers in 1899 refuse to become decrepit and take to the sofa merely because their daughters are grown up, and fathers only require to be amused occasionally in the evening. The new mother may be considerably over thirty-five, bordering on fifty perhaps, but she neither feels aged nor looks it, and is rather inclined to look beyond her home for full scope for her powers when thus set free from maternal cares. And, given intelligence, length of years guarantees experience. One of the tortures of the Inquisition was to place the victim in a room, the walls of which grew nearer to each other every day until, at last, they closed in on him and crushed him to death. In the same way intelligent life gradually grows fainter and fainter as the brain decays for want of exercise. A daily mental constitutional is necessary to prevent the accumulation of what W. K. Clifford called mental fat; mental gymnastics are needed to prevent stiffening of the brain. When not only our habits but our ideas have become fixed, then we have grown old. An octogenarian may be young, if he has preserved the faculty of modifying his conceptions in correspondence with new evidence.