418 DEATH. [BOOK iv. 



begin at the heart or at the lungs or at the brain. In reality, 

 however, when we push the analysis further, the central fact of 

 death is the stoppage of the heart, and the consequent arrest of 

 the circulation ; the tissues then all die, because they lose their 

 internal medium. The failure of the heart may arise in itself, on 

 account of some failure in its nervous or muscular elements, or by 

 reason of some mischief affecting its mechanical working. Or its 

 stoppage may be due to some fault in its internal medium, such 

 for instance as a want of oxygenation of the blood, which in turn 

 may be caused by either a change in the blood itself, as in 

 carbonic oxide poisoning, or by a failure in the mechanical 

 conditions of respiration, or by a cessation of the action of the 

 respiratory centre. The failure of this centre, and indeed that of 

 the heart itself, may be caused by nervous influences proceeding 

 from the brain, or brought into operation by means of the central 

 nervous system ; it may, on the other hand, be due to an imperfect 

 state of blood, and this in turn may arise from the imperfect or 

 perverse action of various secretory or other tissues. The modes of 

 death are in reality as numerous as are the possible modifications 

 of the various factors of life ; but they all end in a stoppage of the 

 circulation, and the withdrawal from the tissues of their internal 

 medium. Hence we come to consider the death of the body as 

 marked by the cessation of the heart's beat whenever that cessa- 

 tion is one from which no recovery is possible ; and by this we are 

 enabled to fix an exact time at which we say the . body is dead. 

 We can, however, fix no such exact time to the death of the 

 individual tissues. They are not mechanisms, and their death is 

 a gradual loss of power. In the case of the contractile tissues, we 

 have apparently in rigor mortis a fixed term, by which we can 

 mark the exact time of their death. If we admit that after the 

 onset of rigor mortis recovery of irritability is impossible, then a 

 rigid muscle is one permanently dead. In the case of the other 

 tissues, we have no such objective sign, since the rigor mortis of 

 other tissues manifests itself chiefly by obscure chemical signs. 

 And in all cases it is obvious that the possibility of recovery, 

 depending as it does on the skill and knowledge of the experi- 

 menter, is a wholly artificial sign of death. Yet we can draw no 

 other sharp line between the seemingly dead tissue whose life has 

 flickered down into a smouldering ember which can still be fanned 

 back again into flame, and the handful of dust, the aggregate of 

 chemical substances into which the decomposing tissue finally 

 crumbles. 



Moreover, the failure of the heart itself is at bottom loss of 

 irritability, and the possibility of recovery here also rests, as far 

 as is known at present, on the skill and knowledge of those who 

 attempt to recover. So that after all the signs of the death of the 

 whole body are as artificial as those of the death of the constituent 

 tissues. 



