THE BLOOD. 161 



recurriilg and prolonged convulsive fits quickly produce 

 exhaustion, and death invariably occurs in the midst of 

 frightful convulsions, in the course of three or four days 

 after manifestation of the first acute symptoms of the 

 disease, treatment being of no avail whatever. 



CHAPTER Vni. 

 The Blood, 



The blood is the great fluid of the body ; it is the life- 

 giving principle, as upon it all vitality depends. The 

 majority of diseases are caused by some change in the 

 blood. It serves to nourish the various tissues of the body, 

 as well as serving to eliminate all effete material. During 

 the day, when the mind and body are actively engaged, 

 waste of the tissues takes place. This waste at night, 

 during rest, is repaired. It has been computed that, during 

 a year, a man receives about three thousand pounds of air, 

 water, food, etc., and wastes the same amount by means of 

 faeces, urine, etc. When the blood ceases to circulate, 

 death results, as in fatal haemorrhage, viz., syncope, or the 

 heart may lose its contractile power through the action of 

 some poison. Again, when the blood ceases to circulate 

 through the lungs, death takes place by asphyxia. In cases 

 where cerebral disturbance interferes with the action of the 

 muscles of respiration, the breathing becomes stertorous 

 and difficult, and death results from coma. The circulation 

 of the blood is carried on by means of the heart, arteries, 

 veins, and capillaries. The arteries are very elastic, and 

 have the power of contractility by virtue of their muscular 

 coat. The veins have numerous valves formed by a 

 doubling of the mucous membrane ; these valves accelerate 

 the circulation of the blood, forcing it onward in the way 

 it should go, and prevent regurgitation taking place. The 



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