1000 SPECIAL PHYSIOLOGY. 



take place through the nervous system, as when a violent shock or 

 concussion is communicated to the body ; it is in this mode, that strong 

 mental emotion, as intense fear, joy, or grief, or sunstroke, lightning, 

 extensive burns of the surface of the body, and sedative poisons, are 

 fatal to life. The effects of many sedative poisons as e. g., of aco- 

 nite, digitalis, and tobacco are produced by the passage of the delete- 

 rious substance into the blood, and by the action of the blood, thus 

 vitiated, on the nerves of the heart. Again, death by syncope may 

 proceed from an enfeebled condition of the heart's substance, so that 

 its contractile power gradually fails, a mode of death which is ex- 

 ceedingly common. It occurs in persons affected with disease of the 

 tissues of the heart, especially in cases of fatty degeneration of this 

 organ. Starvation (p. 909), exhausting diseases, and long-continued 

 violent exertion, are further causes of death from feebleness of the 

 heart's action. Lastly, this mode of death may occur from sudden 

 and profuse hemorrhage, the circulation being arrested, not from loss 

 of the contractile power of the heart, but owing to the insufficient 

 quantity of blood which passes into its cavities. It takes place when 

 a large bloodvessel is wounded, or when it is ruptured owing to disease 

 of its coats, and in cases of profuse internal hemorrhage, as when an 

 aneurism bursts. 



Death by asphyxia, or suffocation, occurs when the movements of 

 respiration, or the access of oxygen to the lungs, are arrested, the flow 

 of blood through the pulmonary capillaries then ceasing. This mode 

 of death occurs in cases of disease affecting the heart and lungs, and, 

 though more rapidly, in choking, strangulation, and drowning. The 

 breathing of carbonic acid and other poisonous gases, also kills by 

 asphyxia ; but this fatal result is due both to the absence of free oxy- 

 gen and to the deleterious properties of the gas. The simple priva- 

 tion of atmospheric air, acts only indirectly on the heart ; for the 

 movements of this organ, and, indeed, even the pulsation of the smaller 

 arteries, continue for a time, although all other signs of vitality have 

 disappeared. The blood, as it traverses the pulmonary capillaries, 

 now no longer undergoes the chemical changes essential to respiration, 

 for it is non-aerated or venous, and cannot therefore sustain the func- 

 tions of the various parts to which it is distributed. At first, it passes 

 freely through the pulmonary veins to the left side of the heart, 

 whence it is distributed through the arteries to the different parts of 

 the body. Its noxious action on the brain is quickly shown by the rapid 

 suspension of its sensorial functions, unconsciousness, and convulsions. 

 The circulation in the pulmonary capillaries is at first gradually re- 

 tarded, and at length totally arrested ; so that the lungs are gorged, 

 and the right side of the heart over-distended with venous blood, 

 which passes into the left cavities of the heart in smaller and smaller 

 quantities. Owing to this diminution in the supply of blood, and 

 to its vitiated quality, the contractions of the heart become gradually 

 more feeble, and finally all the vital actions are arrested. In the first 

 stage of asphyxia, the face is livid, although voluntary, or instinctive 

 and conscious, efforts are made to breathe, but without success. In 

 the second stage, volition and even consciousness are lost, though con- 



