CONTROL OF THE CIRCULATION. 83 



in the body cavity near the spinal column, with fibers running to the 

 internal organs. It is also connected with the cerebro-spinal nervous 

 system. 



3. The heart beat is automatic and rhythmic. 



4. The heart beat is regulated by the sympathetic nervous system 

 and by the vagus nerves. 



5. The blood consists of a liquid, the plasma, in which float the 

 colored and colorless corpuscles. 



6. When blood is shed it coagulates, tending to check its own 

 escape. 



7. Lymph is like the blood diluted and lacking the colored cor- 

 puscles. 



8. A set of lymph tubes conveys the lymph into the veins to join 

 the flow toward the heart. 



9. In its course the lymph passes through the lymphatic glands. 



Questions. I. What makes the hands grow red and puff up on 

 sitting in a warm room after snow balling ? 



2. How is a mustard plaster effective? 



3. Why does light exercise before retiring promote sleep? 



4. Why are the feet often cold after studying? 



5. How does the application of ice, or cold water, relieve head- 

 ache? 



6. Why should the clothing be changed after getting wet? 



7. What is the meaning of humor, in the expressions "good- 

 humored, 1 ' " bad-humored " ? Have these expressions a real physio- 

 logical significance? 



