Screening and Destruction 211 



the end of November, in the rainy season, when 

 malaria incidence is high on the Isthmus, only 

 four cases of malaria occurred among the forty 

 laborers occupying these cars — a weekly incidence 

 of three tenths of one per cent. The difference 

 was due to having a man devote half an hour a day 

 to the destruction of the Anopheles found in these 

 cars. The work cost five cents a day. 



The technic of hand catching is as follows: A 

 glass tube about four and one half inches long 

 and one inch in diameter, of the variety used for 

 packing small camel hair brushes, is used. An 

 inch layer of small rubber bands is packed into the 

 bottom of the tube. They are held in place by a 

 plug of absorbent cotton, which in turn is covered 

 by a disk of blotting paper to facilitate the removal 

 of mosquitoes from the tube, by preventing their 

 entanglement in the cotton. A few cubic centi- 

 meters of chloroform are poured into the tube, 

 which is then covered, and the chloroform allowed 

 to become absorbed by the rubber bands. A tube 

 thus prepared will be lethal to mosquitoes for 

 several days. The chloroform tube has the ad- 

 vantage of being safer than the cyanide tube in 

 the hands of a more or less careless laborer. To 

 catch a mosquito with the tube, the cork is re- 

 moved, and the mouth of the tube quickly placed 



