i The biological clock ii Why dying is beneficial iii The ageing process of men and women iv Prolonging your life v Limitations of life span vi Modes of development of different species vii A stable life span despite improvements viii Energy consumption ix Fundamental differences in ageing of objects and organisms x Repair of genetic material It follows from the above that sparing use of energy reserves should tend to extend life. Experience will show that to live in this way not only increases the life span but is also very healthy.