CHAPTER VI. 

 CIRCULATION OF THE BLOOD. 



The Blood and its Work. There is no bleeding when 

 we trim the nails or cut the hair, and the outer skin has 

 no blood in it. But the inner skin, and almost every tissue 

 within it, if pierced even by the finest needle, yields blood. 

 We know that loss of blood causes weakness, and may 

 soon cause death. 



What kind of a substance is blood ? Why is it so 

 essential to life? How does it do its work? 



The Rate of the Heart Beat The heart beats about 

 seventy-two times a minute. In children it beats faster. 

 The rate is increased by exercise, by heat, by food, and by 

 mental excitement. 



The Heart Beat and the Pulse. i. The heart beat may be felt at the 

 left of the breastbone. \ 



2. The pulse may be felt-at tbe wrist, in the neck beside the wind- 

 pipe, and in various parts of the body. Perhaps the most convenient 

 place to study it is at the temple. Lay the forefinger lightly along the 

 cheek just in front of the ear. Count the pulsations for a minute. 



3. Let one or two pupils step to the blackboard and put down the 

 number of pulsations of each pupil, and divide by the number thus 

 reporting, to get the average. 



4. Let all count the pulse while sitting. Get the average of the 

 class. 



5. Find the pulse while sitting ; rise quickly, and immediately begin 

 to count the pulse. Compare with the pulse as taken while sitting. 



6. Compare the pulse before and after meals. 



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