590 Introduction to the Study of Science 



II. The microorganisms which cause rabies, anthrax, and 

 tetanus gain entrance into the body of man or animal through 

 cuts and abrasions of the skin. Tetanus bacteria are abundant 

 in the soil of certain localities and may infect wounds in the 

 feet or hands when these are contaminated with dirt. A dirty 

 nail or splinter may be infected with the tetanus germ, and, if 

 accidentally forced through the skin, leaves the germ to infect 

 the individual. Dust particles lodging upon the skin may 

 carry pathogenic germs and be driven deep into the flesh by 

 cuts. It is necessary merely to mention the cases of those 

 infected with tetanus through wounds made by percussion 

 caps, firecrackers, and so on. Wounds made by any unclean 

 object should be bathed thoroughly with a disinfectant. 



III. There are certain diseases, the germs of which may be 

 received through the eyes and through sores or breaks in the 

 skin or in the mucous membrane, such as chapped lips. The 

 germs of these diseases may be conveyed by the hands to the 

 face and mouth, by such public utilities as the telephone, drink- 

 ing cups, and towels. 



IV. The animal parasites which cause malaria, dengue fever, 

 and yellow fever are introduced into the body by the bite of 

 mosquitoes, and that causing sleeping sickness by the bite of 

 the tsetse fly. Infantile paralysis may be transmitted by the 

 stable fly or by fleas, though this is far from being established. 

 Bubonic plague is usually transmitted by fleas which attack 

 both human beings and rodents, such as the rat and the ground 

 squirrel. Rocky Mountain spotted fever, a disease now found 

 in all of the Rocky Mountain and Pacific coast states, is trans- 

 mitted by the tick. Typhus fever, often epidemic in military 

 camps, is transmitted by vermin, such as the body louse. Its 

 prevention is a matter of cleanliness and destruction of vermin. 



The hands are active in transmitting disease germs, though 

 this may not at first be suspected. It requires but a little 

 observation to become convinced of the unusual opportunity 

 of hands to transfer infective germs. Note how frequently and 



