of base necessary to shift the acidity or alkalinity in each of the solutions to the 

 same degree as two drops did in the water solutions. Record the results in a table, 

 summarize, and then explain what you understand by the "buffering" actions of 

 these salts. 



5 To find the effect of exercise on the pulse rate, determine the number of 

 heartbeats per minute while at rest, and again after taking exercise. Compare the 

 rate and the intensity of the pulse before and after the exercise. 



QUESTIONS 



1 Of what does human blood consist.^ 



2 In what respects is blood like lymph? In what respects do the two fluids 

 differ? 



3 How does clotting take place? 



4 What do the blood and the lymph do? 



5 How is the blood circulated throughout the vessels of the body? 



6 How does the heart of a frog resemble that of a man? How do the two 

 differ? 



7 What is the advantage of a "double circulation"? 



8 What are the principal changes that take place in the blood? 



9 How is the stability of the blood and of other body fluids maintained? 



10 What compensating reactions take place when muscular activity is in- 

 creased? when an organism is exposed to extreme cold? 



11 How is homeostasis maintained by an acceleration of processes that are 

 continually taking place anyway? 



12 How do "buffer salts" tend to preserve the alkalinity of the blood? 



200 



