l86 TROPICAL MEDICINE AND HYGIENE 



disturbed and increase in other forms of life, possibly 

 harmful, taking place. Something can be done by fumi- 

 gation to destroy the domestic mosquitoes, possibly 

 infected with filaria, during the fortnight or so required 

 for the development of the larvae. 



The most hopeful measures are those that prevent the 

 eggs being deposited in places suitable for their develop- 

 ment. This involves a consideration of the natural means 

 which aid in the destruction of such eggs ; and a modifica- 

 tion of the present means adopted for disposal of faeces, 

 when these are favourable for the propagation of intestinal 

 worms. Wholesale treatment with anthelmintics of 

 persons harbouring entozoal parasites is possible only 

 where people are under constant observation and control, 

 and the apparently healthy person who harbours parasites 

 and distributes the eggs is very difficult to deal with. In 

 mines, where this method has been adopted to some 

 extent, it is found that many persons purge themselves 

 thoroughly before the medical examination, and so, as 

 the eggs are expelled, appear to be uninfected. 



Native labourers usually dispose of their faeces by : 



(1) Deposition of faeces on cultivated lands or in natural 

 bush usually in the vicinity of water. The vicinity of 

 water is important, because, not only is there more cover, 

 as the vegetation is more abundant, but so many native 

 races wash after defaecation. Under such circumstances, 

 they stand in the water and mud in the vicinity of bush 

 used as a latrine ground, so that infection, with ankylos- 

 tomes, and probably schistosomes, is very liable to take 

 place. The deposition of faeces on cultivated or moist 

 earth affords the best possible chance for the development 

 of eggs and larvae. 



(2) Deposition of faeces on dry earth or sand, as is 

 common in the drier tropical countries. The faeces 

 retain the moisture in the part in contact with earth, and 

 the earth underneath is moistened, so that as the larvae 

 hatch out they can escape into the earth. Eggs with 

 thick shells retain their vitality. Probably a much 



