MALARIAL FEVERS 249 



apparent. In general these consist in destroying the 

 breeding-places of mosquitoes when practicable, in 

 destroying the ova and larvae in marshes and pools 

 of stagnant water, and in avoiding the bites of the 

 insects. 



In bodies of water containing minnows and other 

 small fish the larvae of mosquitoes are promptly dis- 

 troyed, as they serve them as food. Frogs also feed 

 upon mosquito larvae. Mosquitoes do not, as a rule, 

 deposit their eggs in running streams and a perfectly 

 smooth surface of water is required for the exit of the 

 adult mosquito from the puparium. It is said that 

 this may be effectually prevented by agitating the 

 surface of the water with a water-wheel put in motion 

 by a wind-mill. There are various temporary exped- 

 ients by which the larvae may be killed in the breed- 

 ing-places of mosquitoes, but evidently the most 

 effectual remedy is to destroy the breeding-places by 

 filling up stagnant pools, filling or draining marshes, 

 and removing all small receptacles of water from 

 the vicinity of dwellings. Rain-water barrels, bottles, 

 tin cans, street catch-basins, etc., all serve as breed- 

 ing places, especially for mosquitoes of the genus 

 Anopheles which serve as the intermediate host of 

 the malarial parasite. As a temporary measure the 

 use of petroleum is to be especially recommended. 

 This quickly spreads out over the surface of bodies of 



