MAN CONSIDERED PHYSIOLOGICALLY. 669 
less adaptation of internal to external conditions, it becomes 
clear that death may be said to be ever imminent; and in the 
highest mammals the vital organism is so complex and so 
delicately balanced, that it is marvelous that life lasts so long 
as it does. Few animals perish from simple decay leading to a 
gradual slowing of the vital machinery, down to zero, so to 
speak; but when death is not due to violence, as it frequently 
is, it rather arises from some essential part getting out of gear, 
either directly or indirectly. So great is the need of a constant 
supply of free oxygen in the mammal, that an arrest of the 
respiration always implies a stoppage of the circulation. These 
results may be brought about by the direct action of poisoned 
blood on the heart, or on the nervous centers presiding over 
lungs, heart, and other organs. Death may then be due to 
central influences, though finally the arrest of the circulation 
is the real proximate cause. When the circulation is so ar- 
rested that it can not be started again, somatic or body death 
must follow, which is to be distinguished from the death of 
the individual tissues. 
Somatic death marks the first stage of the return of a vital 
organism toward the inorganic world, whence it was, in a 
sense, derived. That molecular arrangement or movement 
peculiar to living things once being permanently deranged, 
its resolution into the less complex forms of the inorganic 
compounds speedily follows, though the rate will depend much 
upon circumstances in any individual case. Life is much 
more of a mystery than death. Physiology attempts to de- 
fine the conditions under which life exists, but can not explain 
life itself. "Will it ever lift the veil ? 
