496 



DEFENSES AGAINST DISEASE 



The respiratory trad furnishes a means for the entrance of germs. 

 Spray or droplets of sputum sneezed or coughed out may be 

 breathed in by other people. Germs of pneumonia, diphtheria, 

 scarlet fever, and colds often enter the bo(h' in this wav. 



Certain other organisms enter the body through Avounds or 

 skin abrasions. These skin openings may be of various kinds. 

 Cuts, scratches, torn hangnails, and cracked skin are responsible 

 for the entrance of dirt which may carry not only tetanus germs 

 but, when present, ringworm (a parasitic mold), hookworms, or 

 other pathogenic organisms. Insect bites form openings through 

 which germs may be introduced. The bite of an Aedes mosquito 

 may transmit yellow fever ; the Anopheles mosquito, malaria ; the 

 rat flea, bubonic plague ; the body louse, typhus fever ; and the 

 tsetse fly, x\frican sleeping sickness. The bites of rabid dogs, 

 cats, wolves, and other animals are responsible for hydrophobia. 

 Some organisms enter the body through the eyes. If the eyes 

 are rubbed with an infected hand or dried with an unclean 

 towel, such diseases as trachoma and pink eye may possibly 

 result. 



Safeguards of the body against disease. The best defense of the 

 body is the strong natural resistance that accompanies good health. 

 As long as rules of health are followed, the vitality is likely to be 

 high. Even though bacteria then invade the body the natural 



An unbroken skin is a protection against invading bacteria. If the skin is pricked or other- 

 wise broken, bacteria may enter and cause an infection. 



protective substances and cells tend to control them with success. 

 If resistance is low, due to insufficient air or sunlight, inadequate 



