LIFE: ITS NATUEE, OEIGIN AND MAINTENANCE 35 



terminates in death. The only exception is in the reproductive cells, 

 in which the processes of maturation and fertilisation result in rejuvenes- 

 cence, so that instead of the usual downward change towards senes- 

 cence, the fertilised ovum obtains a new lease of life, which is carried 

 on into the new-formed organism. The latter again itself ultimately 

 forms reproductive cells, and thus the life of the species is continued. It 

 is only in the sense of its propagation in this way from one generation to 

 another that we can speak of the indefinite continuance of life : we can 

 only be immortal through our descendants ! 



The individuals of every species of animal appear to have an average 

 duration of existence.* Some species are known the individuals of 



which live only for a few hours, whilst others survive 

 Average duration of f or a hundred years.! In man himself the average 



length of life would probably be greater than the 

 three-score and ten years allotted to him by the 

 Psalmist if we could eliminate the results of disease and accident ; when 

 these results are included it falls far short of that period. If the terms of 

 life given in the purely mythological part of the Old Testament were 

 credible, man would in the early stages of his history have possessed 

 a remarkable power of resisting age and disease. But, although maoy 

 here present were brought up to believe in their literal veracity, such 

 records are no longer accepted even by the most orthodox of theolo- 

 gians, and the nine hundred odd years with which Adam and his 

 immediate descendants are credited, culminating in the nine hundred 

 and sixty-nine of Methuselah, have been relegated, with the account of 

 Creation and the Deluge, to their proper position in literature. When 

 we come to the Hebrew Patriarchs, we notice a considerable diminu- 

 tion to have taken place in what the insurance offices term the ' expec- 

 tation of life.' Abraham is described as having lived only to 175 

 years, Joseph and Joshua to 110, Moses to 120 ; even at that age 

 ' his eye was not dim nor his natural force abated.' We cannot say 

 that under ideal conditions all these terms are impossible ; indeed, 

 Metchnikoff is disposed to regard them as probable ; for great ages are 

 still occasionally recorded, although it is doubtful if any as consider- 

 able as these are ever substantiated. That the expectation of life was 

 better then than now would be inferred from the apologetic tone adopted 

 by Jacob when questioned by Pharaoh as to his age : ' The days of the 

 years of my pilgrimage are an hundred and thirty years ; few and evil 

 have the days of the years of my life been, and have not attained unto 

 the days of the years of the life of my fathers in the days of their 



* This was regarded by Buffon as related to the period of growth, but the ratio is 

 certainly not constant. The subject is discussed by Kay Lankester in an early work : 

 On Comparative Longevity in Man and Animals, 1870. 



f The approximately regular periods of longevity of different species of animals 

 furnishes a strong argument against the theory that the decay of old age is an 

 accidental phenomenon, comparable with disease. 



