It is clear that for the preservation of health detection of disease in the earliest stage is all-important, and that this can be attained by periodic examination by a medical man; but obvious though this may be, the average man waits to call in a doctor until he knows that he is ill. Timely advice as to methods of life, food and drink, occupation, or environment would often prevent disease and premature death. In 1913 the Life Extension Institute was founded in New York for such periodic examination and report, and the Life Assurance Companies, finding that persons so examined showed, at any rate for some years, a death rate lower than that anticipated, gave it financial support. FUNCTIONAL ACTIVITY As is well known, disuse leads to atrophy, and biologically conditions rendering an animal’s supply of food extremely easy and safe are followed by atrophy of the parts no longer necessary in a state which may thus come to border on parasitism; in an extreme degree this result is shown in barnacles (degenerated crustaceans) and ascidians (degenerated vertebrates). In man the cessation of an active life on retirement to the country, described by Samuel Johnson as “a kind of mental imprisonment,” or the sudden acquisition of wealth, often exerts a most evil influence; for if the whole body is no longer kept in a condition of functional activity, those parts allowed to remain relatively idle begin to degenerate and atrophy; loss of function means a diminished blood supply and nutrition, and so degenerative atrophy. According to Laurentius “nothing hastens old age more than idleness.” James Easton,[64] who collected 1712 records of centenarians, many of them open to criticism, endorses Hufeland’s dictum that no idler has ever attained to a remarkably great age; and Sir Thomas Browne’s[65] quaint injunction “Dull not away thy days in sloathful supinity and the tediousness of doing nothing” is old but true wisdom.