HAY FEVER 



69 



and dirt without charging the air with it is the best method. 

 Floors should be wiped with a damp or oily cloth rather 

 than swept. Why? An interesting problem would be 

 this : To determine which method of cleaning in the 

 home is the most hygienic. Suggest four methods of clean- 

 ing and consequently four different conditions under which 

 you could expose prepared Petri dishes in your own home. 



How the organs of respiration are protected from dust. 

 The nose, the organ of smell, performs several other very 

 important offices. Just near its entrance are 

 many hairs which the air must pass. Down 

 below, in the throat itself, is a soft lining of 

 cells which are provided with tiny whip-like 

 structures made of living matter. These 

 structures, called cilia, are constantly in mo- 

 tion, and always whip upwards so as to ex- 

 pel all foreign material from the lungs. The 

 ciliated cells, together with the hair in the 

 nose, prevent most foreign matter, such as dust 

 and dirt with their load of germs, from going 

 down into the lungs. The lining of the nose also moistens 

 and warms the air before it passes to the lungs. 



Hay fever. Dust, however, often causes us trouble. 

 The disease known as hay fever seems to be caused by dust 

 made up of pollen from different kinds of flowers. This 

 pollen is a violent poison to some people, and causes 

 sneezing, itching eyes and nose, and a feeling of dis- 

 comfort. Sometimes relief is obtained by means of spray- 

 ing the air passages, or plugging the holes in the nose with 

 medicated absorbent cotton, but so far no real cure has 

 been found except by inoculation with various vaccines 

 made from the agents which cause the trouble. 



The tubes lead- 

 ing into the 

 lungs are pro- 

 tected from 

 dust by means 

 of ciliated 

 cells. 



