HYGIENE OF THE CIRCULATORY SYSTEM 167 



in many other parts of the body. They are made of fibrous 

 tissues interspersed with numerous spaces. In these spaces, white 

 corpuscles collect and multiply by division. Bacteria are frequently 

 brought to the lymph nodes, w^here they are destroyed by the pha- 

 gocytes, germ-killing white corpuscles, which are found in such num- 

 bers in the lymph nodes that they have little difficulty in destroy- 

 ing bacteria. Occasionally, bacteria escape from the nodes and 

 travel through the lymph into the blood and thus spread infections. 

 If bacteria multiply rapidly and cause an infection in a lymph 

 gland, a wall of calcium is sometimes deposited around the germs. 

 This prevents the bacteria from escaping into the system. A 

 gland of this kind can be cut out and thus the infection is re- 

 moved. A lymph gland acts as a sieve to remove bacterial and 

 foreign materials and thus prevents many injurious substances from 

 getting into the blood and returning to the heart. The lymph 

 glands of miners frequently become clogged with dirt and, there- 

 fore, become greatly enlarged. 



Hygiene of the circulatory system. Blood vessels are kept in 

 tone and the blood is kept circulating normally by regular exercise, 

 fresh air, good food, hot and cold baths, and sufficient sleep. A large 

 part of the repair of the body takes place during sleep. Many red 

 corpuscles are made at this time. If one does not get enough sleep, 

 pallor may result, which is due to an insufficient number of red cor-, 

 puscles. This may cause anaemia. Regular exercise is better than 

 spasmodic exercise. When a person does not exercise sufficiently, 

 the heart and arterial muscles become weak and the muscles all 

 through the body lose their tone. Afiy unusual exercise will then 

 cause palpitation of the heart. Violent emotions overstimulate the 

 heart and blood vessels. Occasionally, this causes the rupture 

 of a blood vessel. A violent fit of anger has been knowm to cause 

 a condition of this kind. Drinking water is invaluable in aiding 

 the blood to give off waste materials collected from the cells, into 

 the organs of excretion ; namely, the lungs, skin, and kidneys. 



