PREVENTION OF COMMUNICABLE DISEASES 239 



body of the mosquito, these parasites pass through definite 

 stages in their life history; and when they reach tin- 

 blood of man, the remaining stages are completed. Thus 

 a man, or an animal, and a particular mosquito are neces- 

 sary for the complete life history of the malarial parasite. 

 This means in addition that for the prevention of 

 malaria all that is necessary is to destroy the Anopheles 

 mosquito, or in case this cannot be done, to screen ade- 

 quately the houses, tents, and bedrooms in the regions 

 where the mosquitoes live. It is interesting to note that 

 this discovery of the cause of malaria and the methods for 

 its prevention was more than anything else responsible for 

 the successful completion of the Panama Canal. The con- 

 struction of this important work was more a health than 

 an engineering problem. 



181. Other Protozoan Diseases. — Other protozoan dis- 

 eases are produced in the same manner as malaria. The 

 carrier may be different, but the principle of spreading 

 the diseases is the same. Yellow fever, for instance, is 

 spread by another kind of mosquito, and sleeping sickness 

 by the tsetse fly. 



182. Hookworm Disease. — This disease is caused by a 

 parasite which is classified as one of the worms. Hook- 

 worm disease belts the earth in a zone which extends thirty - 

 three degrees each side of the equator. Great progress 

 is being made in the United States in curing those su lin- 

 ing from this disease. The wearing of shoes and the use 

 of a sanitary closet are usually sufficient preventives bo 

 protect the people who live in a hookworm district. 



183. Prevention of Communicable Diseases. — The pre- 

 vention of these diseases depends upon an understanding 

 of the causes which produce them, close adherence to the 

 laws of hygiene, and especially the exercising of proper 

 care in the production and cooking of our food. Germ 



