737 
i 879 *J or the Natural Duration of Life . 
twenty. We turned to the dog, to find full maturity at two 
years of age, full life at ten. We turned to the cat, to find 
full maturity at eighteen months, full life at seven and a 
half years. We turned to the rabbit, to find full maturity 
at one year, full life at five. 
“ From these contemplations our minds very naturally 
reverted to the animal, man, to the members of the human 
family. Man, we learned, follows the same rule as the rest 
of living beings. Judged by the same test, his full maturity 
and full age may be calculated with equal precision. His 
maturity — perhaps not quite the full maturity — is twenty 
years. His full age, therefore, is one hundred years. This 
is the anatomical estimate of human life, the surest and by 
far the best of all that can be supplied, since it defines a 
law irrespective of and over-riding all those accidental 
circumstances of social and physical storm and strife which 
may interfere, and indeed do interfere, with every estimate 
based on the career of life itself, as it is shown in the 
ephemera by and through whom it is phenomenally demon- 
strated.” 
“ This lesson,” Dr. Richardson continues, “ struck Mr. 
Chadwick and myself with singular force. On a surer basis 
than we ever trod, it corroborated a view we had ourselves 
promulgated from entirely different stand-points : and it 
further corroborated a similar view which had been advanced 
by our eminent friend, Dr. William Farr. We were led, in 
a word, once again, to the inevitable conclusion that man, 
even in this stage of his probation on the planet, is naturally 
destined to walk upon it, endowed with sensibilities of life 
and intelligence, for a period of one hundred years, and 
that until he realises this destiny practically he is — in value 
of physical life — actually degraded far below his earth- 
mates whom he designates the brute creation, and over 
whom he presumes to exercise his, to them, almighty will. 
“ To certain parts of the scheme of natural life there is 
a boundary. The period of maturity of development has 
its boundary of twenty years,— when the body, as Flourens 
says, ceases to grow ; but if it ceases, in the ordinary sense 
of the term, to grow, it does not cease to increase ; its nu- 
trition improves and perfects for twenty years more at least, 
and then only has reached its completed physical condition. 
It should never from that period gain in weight, and for a 
long time it should not lose. It goes on now through a 
third period, which Flourens admirably calls the period of 
invigoration, during which all its parts become firmer, all 
its functions more certain, all its organisation more perfect; 
