CH. VI.] OLD AGE AND DEATH. 357 



the action of the heart after removal of the head ; or in those 

 in which the vital spirits remain for a lengthened period dif- 

 fused through other portions of the nervous system. Thus, 

 merely animal life may continue after the removal of both the 

 heart and the brain. 



714. Fourthly, an animal is absolutely dead, when its entire 

 system of animal machines is rendered wholly incapable of per- 

 forming its functions (639) . But so long as the structure of that 

 system is not completely destroyed or changed, or the vital spirits 

 contained in it exhausted, so long, in short, as any portion of the 

 system retains the property of duly responding to impressions, 

 the animal is not absolutely dead. It is thus we understand, 

 how animals may be frozen, and yet retain animal life. (Vide 

 Spallanzani.) 



715. The destruction, division, or injury of portions of the 

 system of animal machines, and the exhaustion of the contained 

 vital spirits, are necessarily followed by the complete death of the 

 whole organism, when the primary vital forces of one or both 

 centres of animal forces are abolished (711 — 713). Hence 

 mortification, or the loss of entire limbs, only causes death, 

 when it involves one or other of these centres. 



716. Lastly, death is absolutely complete, when those im- 

 pressions are no longer made on the animal machines which 

 maintain the primary animal functions. Thus, if the heart 

 becomes empty from haemorrhage, its movements cease, the 

 natural stimulus derived from the blood being wanting. Death 

 will not take place, however, so long as either of the primary 

 vital forces are kept active, in some degree at least, by 

 supplying the defective impressions : and this is the art of 

 restoring persons to life apparently dead ; for all animals, 

 whether sentient or insentient, which perish suddenly, as those 

 drowned, frozen, strangled, stunned, suffocated, &c., die from a 

 want of those natural impressions that excite the primary vital 

 forces to the performance of their functions. 



717. Sentient animals may die in any of the modes in which 

 absolute animal death occurs, but none of these are necessary 

 for proper animal death, or the disseverance of soul and body, 

 because animal life may continue after the latter has taken 

 place (708), just as it existed in the earliest germ independently 

 of mental life (634); and a sentient animal may thus be capable, 

 after death in the ordinary sense has taken place, of those 



