696 DEATH. [BOOK iv. 



respiratory centre ; and death may come from the arrest of either 

 of these. As Bichat put it, death takes place by the heart or by 

 the lungs or by 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 me- 

 chanical 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 mechan- 

 ical 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, a cessation 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 simple protoplasm 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 experimenter, 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 decom- 

 posing 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. 



