WOUK AND WASTE. THE BLOOD. 55 



coagulate, by pressing on the spot so as to check the flow. 

 Sometimes it is necessary to tie a handkerchief or a string 

 around the limb above, or sometimes below, the wound. 

 In this case the bandage should not be kept on too long, 

 as other parts of the limb may suffer from want of blood. 



13, Loss of blood causes great weakness, and at length 

 fainting. When we faint, the heart almost stops its action, 

 and the flow of blood becomes very slow. This gives it 

 an opportunity to coagulate, and stop up the bleeding 

 vessels. When the flow of blood can not be stopped, a 

 fainting-fit may save life. 



14, The body of a man contains six or eight quarts of 

 blood. The loss of more than half of his blood would 

 be certainly fatal, and the loss of a very much smaller 

 portion might be so. 



15, People near to death from loss of blood have some- 

 times been restored by throwing into their veins blood 

 drawn from another person. This is called transfusion. 

 It is a delicate and dangerous operation, and not often 

 useful. 



16, Some causes of impure blood are, 



1. Bad air. 



2. Lack of exercise. This makes the flow sluggish. The 

 organs whose' work it is to purify it become inactive. 

 Waste matter accumulates. 



s. Too much or too rich food. The blood becomes loaded 

 with matters which the system can not use and can not 

 easily get rid of. 



4- Too little or too poor food. The blood becomes thin, 

 and unequal to the nourishment of the body. 



5. Alcohol, which is itself an impurity, and unfits the 

 blood for its work. 



