28 ELEMENTARY PHYSIOLOGY less. 



Hence it is that, for a while after what is ordinarily 

 called death, the muscles of an executed criminal may 

 be made to contract by the application of proper stimuli, 

 and the heart may even be excised and made to beat for 

 a considerable time. The muscles are not dead, though 

 the man is. 



13. Modes of Death. — The modes in which death is 

 brought about appear at first sight to be extremely varied. 

 We speak of natural death by old age, or by some of the 

 endless forms of disease ; of violent death by starvation, 

 or by the innumerable varieties of injury, or poison. 

 But, in reality, the immediate cause of death is always 

 the stoppage of the functions of one of three organs ; 

 the cerebro-spinal nervous system, the lungs, or the heart. 

 Thus, a man may be instantly killed by such an injury to 

 a part of the brain which is called the spinal bulb or 

 medlllla oblongata (see Lesson XI.) as may be 

 produced by hanging, or breaking the neck. 



Or death may be the immediate result of suffocation by 

 strangulation, smothering, or drowning, — or, in other 

 words, of stoppage of the respiratory functions. 



Or, finally, death ensues at once when the heart ceases to 

 propel blood. These three organs — the brain, the lungs, and 

 the heart — have been fancifully termed the tripod of life. 



In ultimate analysis, however, life has but two legs to 

 stand upon, the lungs and the heart, for death through 

 the brain is always the effect of tlie secondary action of 

 the injury to that organ upon the lungs or the heart. 

 The functions of the brain cease, when either respiration 

 or circulation is at an end. But if circulation and respira- 

 tion are kept up artificially, the brain may be removed 

 without causing death. On the other hand, if the blood 

 be not aerated, its circulation by the heart cannot pre- 

 serve life ; and, if the circulation be at an end, mere 

 aeration of the blood in the lungs is equally ineffectual for 

 the prevention of death. 



With the cessation of life, the everyday forces of the 

 inorganic world no longer remain the servants of the 



