SPOROZOA 781 



require no more than ten days to complete their three molts. The 

 female alone sucks blood, the male living on fruit and vegetable juices. 

 Egg-laying does not take place until after a meal of blood, and it is 

 possible that the female journeys fairly long distances to obtain this 

 food, and that the first flight, from breeding place to human habita- 

 tions, may be longer than subsequent flights. In general the flight is 

 short, not over three hundred yards, and Gorgas found, in Panama, 

 that a clearing of that width about houses gave ample protection. 



The incubation period of the parasite in the mosquito is about 

 twelve days, after which the insect remains a carrier during the rest 

 of its life, and as the health of the mosquito is unaffected, this may 

 be for two months or more. 



Epidemiology. Since malaria is conveyed solely by the bite of. an 

 infected anopheline, the epidemiology is comparatively simple. In 

 practice, nevertheless, the prevention of the disease is extremely diffi- 

 cult ; but it is the same for all forms of malaria. It must be attacked 

 from all possible angles and the following are the main points to be 

 observed : 



1. Screened houses afford, perhaps, the simplest form of protec- 

 tion, and in beginning work in a new, badly infected place, should 

 be the first thing provided, since they afford a place of security in an 

 otherwise dangerous area, where the workers may take refuge until 

 the situation is under control. This method alone has given magnifi- 

 cent results in Italy (Celli) since it was first used experimentally by 

 Sambon and Low in the Roman Campagna. The screens, to be dur- 

 able, must be of bronze and not iron, and of a fine mesh ( 20 strands 

 to the inch), and should be placed, not on windows and doors, but on 

 the outside of porches and balconies; doorways should have screened 

 vestibules. 



In default of metallic house screens, bed nets may be used, al- 

 though they are not very satisfactory, since one must retire at dusk 

 to be protected. In default of both screens and bed nets, something 

 may be accomplished, temporarily, by daily mosquito catching, and 

 in Panama the method has given remarkable results. A native, 

 armed with a small acetylene lantern and a few catching bottles, 

 soon becomes expert, and can capture each day all the mosquitoes in 

 a number of dwellings. In this way very few anophelines escape cap- 

 ture long enough to become infective for man. Chloroform catching 

 bottles are easily prepared by packing a half ounce of small rubber 

 bands, cut up finely, into the bottom, and pouring in as much chloro- 



