The Campaign in Havana 253 



with paper to prevent the escape of the fumes. 

 Where the leakage was extensive it was not 

 effective. 



In the experimental work it was observed that 

 there were most dead mosqtdtoes per unit of 

 area near the source of light. It was also noticed 

 that before they were overcome by the fumes of 

 pyrethrum many of them pulled off one or more 

 of their legs, but that this did not occur when 

 fumigating with sulphur, tobacco, or formalde- 

 hyde. Pyrethrum powder deteriorates rapidly 

 when stored in a humid tropical atmosphere. 



The proprietors of tobacco warehouses and 

 shops objected to pyrethrum fumigation of their 

 premises because of the odor, and experiments 

 were made to determine the value of tobacco 

 stems as a culicide for Aedes calopus. It was 

 found that the results from its use were equal to 

 sulphur, and the tobacco merchants reported no 

 harmful effect or deterioration of value in the 

 stored tobacco and tobacco products. 



It "was found that sulphur ftimes injured all 

 ordinary metals, unless they were protected by 

 vaseline or some other greasy substance; and that 

 it bleached and stained many fabrics, and stained 

 certain painted surfaces. Pyrethrum only stained 

 some materials slightly, but left an odor. 



