CHAPTER XVIII 



HYGIENE OF THE BLOOD AND THE CIRCULATION 



Questions. 1. How can nosebleed be stopped? 2. How should bleed- 

 ing from a wound be stopped ? 3. Why does the doctor feel the pulse ? 

 4. Why does the doctor listen to the heart ? 



154. The health of the blood. The condition of the blood de- 

 termines the life conditions, and so the health, of all the cells 

 and tissues of the body. To keep the blood in suitable condi- 

 tion we must supply it with plenty of water, with suitable food 

 in right quantities, with necessary salts, and with oxygen ; and 

 we must give the blood a chance to get rid of carbon dioxid and 

 the other waste substances that it gathers from all parts of the 

 body. This is but another way of saying that we must eat 

 properly, breathe properly, exercise properly, rest and sleep 

 properly, and so on. There is no special food for the blood. The 

 blood is the medium through which the food of the body is con- 

 veyed from the food tube (digestive tract) to the living cells. 

 There is no special way of breathing or exercising for the sake 

 of the blood. The body behaves as a whole, and the blood is one 

 of the means of unifying the many different parts. At the same 

 time it is true that the body may be injured by way of the blood, 

 just as it may be injured by way of the mouth or the lungs. 



155. Cuts and wounds. Small wounds will usually stop bleed- 

 ing because of the clotting of the blood (see section 148). For- 

 merly the festering of sores and cuts was looked upon as a 

 normal and necessary condition of healing. Now we know it to 

 result from the action of various kinds of microbes, some of 

 which, at least, produce serious blood poisons (see page 303). 

 To prevent the festering of a wound, and to prevent the invasion 

 of the body by more injurious microorganisms, it is well to treat 



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