CHAP, iv.] DEATH. 1159 



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 ner- 

 vous or muscular elements, or by reason of some mischief affect- 

 ing 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 poison- 

 ing, 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 

 at least 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 per- 

 verse action of various secretory or other tissues. The modes 

 of death are in reality as numerous as are the possible modifica- 

 tions of the various factors of life ; but they all end in a stop- 

 page 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 when- 

 ever that cessation 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 ma*rk the exact time of their death. If 

 we admit that after the onset of rigor mortis recovery of irrita- 

 bility 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 experimenter, is a wholly artificial sign of 

 death. Yet we can draw no other sharp line between the seem- 

 ingly dead tissue whose life has flickered down into a smoulder- 

 ing 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 si^ns of the death of 

 the whole body are as artificial as those of the death of the con- 

 stituent tissues. 



