DEVELOPMENT AFTER BIRTH AGES AND DEATH 859 



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 diminishes, and 

 death follows as an inevitable consequence of life. In old age the mus- 

 cular movements gradually become feeble ; the bones contain an excess 

 of inorganic matter; the ligaments become stiff; the special senses 

 are usually somewhat obtuse ; and there is a diminished capacity for 

 mental labor, with more or less loss of 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 essential to life 

 gives way, and that this is the immediate cause of death, or that an old 

 person is stricken down by some disease to which his age renders him 

 peculiarly liable. It is so infrequent to observe a perfectly physiological 

 life continuing throughout the successive ages of man, that it is difficult 

 to present a picture of physiological death ; but it sometimes occurs that 

 there is a gradual fading away of vitality in old persons, who die without 

 being affected with any special disease. It also is 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. 

 The tissues usually die successively and not simultaneously, nearly all 

 being dependent on the circulating, oxygen-carrying blood for the main- 

 tenance of their physiological properties. It has been demonstrated, 

 indeed, that the properties of tissues may be restored for a time, after 

 apparent death, by the injection of blood into their vessels. 



After death there often is a discharge of the contents of the rectum 

 and bladder ; and parturition, even, has been known to take place. The 

 appearance which indicates growth of the beard after death is probably 

 due to shrinking of the skin and, perhaps, contraction of the smooth mus- 

 cular fibres attached to the hair-follicles. The most important phenom- 

 enon, however, observed before putrefaction begins, is a general rigidity 

 of the muscular system, or rigor mortis, which has already been de- 

 scribed. 



