SENESCENCE, DECADENCE, AND DEATH 423 



more and more difficult. The life of the higher animal 

 rests upon a tripod consisting of the three fundamental 

 functions circulation, respiration, and innervation. 

 These are indispensable functions, the suspension of any 

 one of which causes somatic death in a few moments. 

 We do not say, however, that the individual is dead until 

 all three functions have ceased. There are other func- 

 tions whose suspension is equally fatal, though the end 

 is approached more slowly. Thus should the kidneys 

 be removed, their arteries ligated, or their function 

 otherwise set aside, death is inevitable, nothing can 

 possibly save life, but the end is approached gradually 

 and comes after much suffering through the final inter- 

 ruption of either the circulation, the innervation, or the 

 respiration. 



The tissues and their component cells continue to live 

 on for some time after somatic death has occurred, the 

 actual duration of life depending upon their individual 

 vitality and the quantity of absorbable and still utilizable 

 nutrient juices available. 



There is great dissimilarity among the different tissues 

 in this particular. The nervous tissues seem to die 

 quickly; the muscular tissues preserve their contractile 

 power for some time. The epithelial cells of the skin 

 and of the hair follicles seem to live for some days, so 

 that it is quite possible for the hair to grow a few milli- 

 metres after death perhaps in some cases even more. 

 Soon after death certain chemical changes set in and 

 poison those cells that might otherwise survive longer. 

 Such are responsible for the rigor mortis or stiffness of 

 the muscles brought about by coagulation of the myosin. 



As we descend the scale of animate life, we find a 

 general tendency toward the prolongation of molecular 

 life after somatic death. This can probably be explained 

 by the differing chemical conditions in the bodies of the 

 lower forms. 



Thus in the familiar superstition that a dead snake 

 moves its tail "till sundown," and in the tendency for 



