534 Introduction to the Study of Science 



SUMMARY 



Malaria is typical of the diseases that have been brought under 

 control by scientific knowledge. 



Malaria is supposed to have been the cause of the decline of some 

 ancient peoples. 



The conquest of a disease depends upon the knowledge of its 

 cause, transmission, and control. 



In the study of malaria its cause was discovered to be an animal 

 parasite in the human blood. 



Because one stage of its life history was missing in the human 

 blood, search for it was made in blood-sucking insects, particularly the 

 mosquito. 



Traces of the parasite were found in the Anopheles mosquito. 

 This discovery led to the working out of the complete life history of 

 the parasite. 



The theory of the transmission of malaria by the mosquito was 

 put to practical tests by showing : (1) that persons could live in " malarial 

 swamps " without contracting the disease if they were protected from 

 mosquitoes ; (2) that persons not in malarial regions contracted 

 malaria when bitten by an infective mosquito. 



The conquest of malaria illustrates the way in which men who are 

 scientific in spirit and method attack and solve problems concerning 

 human welfare. 



The control of infectious diseases depends first upon the preven- 

 tion of the transmission of the germs to uninfected persons, and 

 second, upon the destruction of the germs or the neutralization of 

 their toxins in infected persons. 



Yellow fever was conquered by preventing the transmission of the 

 germs, by means of the destruction of the Stegomyia mosquito. 



The cause and means of transmission of infantile paralysis are 

 problems under investigation. 



REVIEW QUESTIONS 



1. Why is the study of malaria important? 2. Why was this 

 name given to the disease ? 3. When did the discussion of living dis- 

 ease germs begin? State the theories then advanced. 4. What was 

 Laveran's contribution to the knowledge of malaria? 5. Give an 

 account of the discoveries of Golgi. 6. Describe the chief types of 

 malaria. 7. What was Manson's theory of its transmission ? 8. State 

 the problem as presented to Ronald Ross. 9. Give an account of the 



