As to medico-legal aspects, eccentricities may prevent the aged testator from being allowed the right of testament, but in general the mental symptoms of advanced senility differ from senile dementia only in degree. As to the future of old age, those who are not senile have a distinct place as counsellors. They should excel in strength of reason, cool judgment, and breadth of view. One may be past the age of discretion before one is old in years. The conservative tendencies of this period are valuable as checks to the exuberant impulses of youth. The dependent aged are a burden and their support is often a handicap. With modern progress the number who fail to keep pace increases with the speed of advance and this has to be complemented by the fact that the old are increasing in numbers. With few exceptions man lives longest of any animal. Everything does grow old except vanity and the more perfect the organization the earlier the aging and the sooner the end, for it is the perfect more surely than the good that die young. Every stage of life is marked by a limit, but this limit varies greatly. “Every man past forty is a fool, physician, or a divine, and most people practically throw away their lives.” The lower the scale of education, the greater the hazard of life. Longevity among pure muscle workers is rare. We know little of the influence of race, but we know that women, lean people, the married, the religious, on the whole, live longest. Haeckel believed in “medical selection” and pointed to the fact that some have greater power to resist disease. Is this desirable for the integrity of the race? “Death is a process, not an event.” Man does begin to die early in life. The bicycle rider has to keep going to keep erect, and so the old must keep working. The first vacation is often fatal. Hastings Gilford[147] regards the development of the human body as a whole, or of any portion of the body, as describing a curve that ascends from the time of the union of the two genetic elements to a maximum at which there is the greatest development of specialization in function and the least in the general characters, such as those of multiplication. The curve then begins to descend, with a gradual and progressive loss of differentiation in form and function and an increasing tendency of certain cells to multiply. Decay of certain cells during advancing age leads to their becoming bodies foreign to their host, and this, in turn, calls forth the phagocytes which, walling off the foreign body, become themselves transformed into fibrotic tissue. The three characters of old age are decay, fibrosis, and proliferation of non-specialized cells. As the more specialized cells retrogress, with the loss of specialization they take on an increased tendency to multiplication. “Reversion ... is the keynote of the proliferation in old age wherever it occurs.”