114 HUMAN BIOLOGY 



160. A study of the pulse. Laboratory and home study, 



A. To take the pulse. (Laboratory study.) 



1. Place the fingers on the wrist as directed in 158, 

 and count the pulse while sitting quietly for a 

 minute, being careful not to miss any of the beats. 

 Repeat the count several times, until the numbers 

 approximately agree. Describe what you have 

 done, and record your pulse rate in your note- 

 book. 



2. (Optional.) In a table like the following record the number 

 of pupils with a pulse rate (while sitting still) correspond- 

 ing to the headings of the various columns named below 

 40-49 | 50-59 | 60-69 | 70-79 | 80-89 | 90-99 | 100+ 



B. To determine the effect on the pulse rate of different posi- 



tions of the body. (Homework). 



1. Lie a few moments on a couch and completely relax 



the muscles. Count and record your pulse, re- 

 . peating the count till the number during a minute 

 is reasonably constant. (It is better, if possible, 

 to have some one else do the counting.) 



2. In a similar way, make a record of your pulse while 



sitting. 



3. Determine, likewise, the pulse rate when you are 



standing. 



4. Take some vigorous exercise for a few moments (e.g. 



running upstairs or riding a bicycle). 1 Now de- 

 termine your pulse rate. 



5. What do you conclude, therefore, as to the effect on 



the heart beat of vigorous muscular activity? In 

 what ways may the rate of the heart beat be de- 

 creased? 



161. Valves at the mouth of arteries. The aiteries are 

 always full of blood, and when the ventricles contract, these 



1 In case the pupil has any heart difficulty, a milder form of exer- 

 cise, such as walking rapidly or swinging the arms, should be taken. 



