the City of Havana alone was wiped out in a few months, 

 the building of the Panama Canal was made possible, and 

 tropical America was rendered habitable for the white race. 

 Malaria, our principal insect-borne disease, is held re- 

 ly- . sponsible for an annual money loss of 



^Malaria $ 100 > 000 > 000 in the United States alone. 

 It is transmitted by the bite of the Anopheles 

 mosquito, which breeds in pools of stagnant water and woody 

 sluggish streams. The adult mosquito of this type can be 

 distinguished from the common or Culex mosquito by the 

 fact that its wings are spotted and by its posture when 

 lighted. Its body stands out in a straight line at an angle 

 to the surface on which it rests, while the body of the com- 

 mon mosquito stands in a humpbacked position, with the 

 posterior part of its body roughly parallel to the wall or 

 ceiling. 



The control of malaria depends on the elimination of 

 breeding places by drainage of swamps, by cutting out and 

 clearing ditches, streams and pools, and by the elimination 

 of small receptacles of stagnant water. Mosquito larvae, 

 or "wigglers," may be destroyed by the use of oil or poison- 

 ous larvicides or by stocking ponds with fish, which feed upon 

 them. Adult mosquitoes should be kept out of houses, and 

 particularly excluded from malaria patients by screening, 

 and in seriously infected regions, quinine should be system- 

 atically employed as a prophylactic. 



SPREAD OF DISEASE BY CONTACT 



While the diseases carried by food and by insects have in 

 r , large measure been brought under control, 



_. the diseases which are chiefly spread by 



contact, particularly such diseases as diph- 

 theria, measles, scarlet fever and whooping cough, which are 

 disseminated by the discharges from the nose and throat, 

 have been much less successfully controlled. The methods 



34 



