Insects and Human Health 535 



efforts of Ross, and their results. 10. Where did he find the missing 

 stage in the life history of the mosquito? 11. What did this dis- 

 covery mean in the conquest of the disease ? 12. How did the knowl- 

 edge of the cause of malaria and its transmission influence the investi- 

 gation of yellow fever and other diseases? 13. What other insects 

 are disease carriers? 



14. Describe the life history of the malarial parasite in man, ac- 

 counting for its introduction, its source of food, the fate of the red 

 corpuscles of the blood, and the effect of the parasites' waste prod- 

 ucts upon the patient. 15. Give an account of its removal from 

 man ; its course of development in the mosquito. 16. In what ways 

 may the parasites be distributed by the mosquito? 17. Explain how 

 an outbreak of malaria may occur without a new inoculation by mos- 

 quitoes. 



18. (a) Describe the practical tests of Ross's theory of malarial 

 transmission, made in the malarial district in Italy. (6) What did 

 they prove? 19. Describe the practical test of the theory made in 

 England. What was proven? 20. How do men of scientific habits 

 of work deal with. a problem? 21. What is the value of practical 

 tests of a proved theory? 22. How may the malarial parasite be 

 controlled or destroyed in man? 23. What knowledge is necessary 

 for the prevention of the transmission of malaria? 24. What lessons 

 does the conquest of malaria teach as to the control of infectious 

 diseases and the prevention of their transmission ? 



25. Give an account of the conquest of yellow fever. 26. Why is 

 infantile paralysis an important problem to-day ? 27. What is known 

 of the cause of the disease ? 28. What is known of its ways of trans- 

 mission ? 



II. THE MOSQUITO 



263. Relation to human health. As already stated in the 

 study of malaria, the Anopheles mosquito is widely distributed 

 in the United States as well as in other countries. In the past 

 it has wrought great disaster to human health and life ; but 

 to-day in many localities, where malaria was formerly prevalent, 

 scarcety a case can be found because of the relentless war of 

 extermination waged against this mosquito. The Panama 

 Canal Zone, where in the past yellow fever and malaria made 

 human occupation almost impossible, is now become as safe as 

 any place on earth, through intelligent use of preventive measures 



