460 GENERATION. 



opment at about the age of thirty-five, and he begins to de- 

 cline after the sixtieth year, although such a rule, as regards 

 intellectual vigor, would certainly meet with numerous ex- 

 ceptions. 



We do not propose to consider, in this connection, the 

 psychological variations which occur at different ages, but, as 

 regards the general process of nutrition, it may be stated, in 

 general terms, that the appropriation of new matter is a little 

 superior to disassimilation up to about the age of twenty-five 

 years ; between twenty-five and forty-five, these two processes 

 are nearly equal ; and, at a later period, the nutrition does not 

 completely supply the physiological waste of the tissues, the 

 proportion of organic to inorganic matter gradually dimin- 

 ishes, and death follows, as an inevitable consequence of 

 life. In old age, the muscular movements gradually become 

 feeble ; the bones contain an excess of inorganic matter ; the 

 ligaments become stiff ; the special senses are usually obtuse ; 

 and there is a diminished capacity for mental labor, with 

 more or less loss of the memory and of intellectual vigor. 

 It is a curious fact that remote events are more clearly and 

 easily recalled to the mind in old age, than those of recent 

 occurrence ; and, indeed, early impressions and prejudices 

 then appear to be unusually strong. 



It frequently happens, in old age, that some organ essen- 

 tial to life gives way, and that this is the immediate cause of 

 death ; or that an old person is stricken down by some dis- 

 ease to which his age renders him peculiarly liable. It is so 

 infrequent to observe a perfectly physiological life, continu- 

 ing throughout the successive ages of man, that it is almost 

 impossible to present a picture of physiological death ; but 

 we sometimes observe a gradual fading away of vitality in 

 old persons, who die without being affected with any spe- 

 cial disease. It is also difficult to fix the natural period 

 of human life. Some persons die, apparently of old age, 

 at seventy, and it is rare that life is preserved beyond one 

 hundred years. In treating of the so-called vital point, we 



