SUMMARY AND CONCLUSIONS 261 



some outbreaks Morgan's bacillus is very frequently present in 

 the faeces of children suffering from the disease, and it is very 

 significant, that while it has been found not uncommonly in the 

 intestines of flies associated with such outbreaks, it seldom occurs 

 in the intestines of flies from non-diarrhoea infected localities. 



The annual mortality due to this disease is so great that a 

 serious attempt to conclusively ascertain the part played by flies 

 in its dissemination by exterminating them in some suitable 

 areas, usually exhibiting a high mortality, though expensive, 

 would be justified (Chapter XIV). 



Most of the evidence relating to the spread of cholera by flies 

 is somewhat old, but is so remarkable that careful investigation 

 of this problem is highly desirable (Chapter XV). 



Flies are greatly attracted to tuberculous sputum, and can 

 carry and distribute B. tnberadosis contained in it for several 

 days. Whether they are serious factors in the spread of the 

 disease yet remains to be proved (Chapter XVI ). 



Flies feeding on blood containing non-spore-bearing anthrax 

 bacilli can carry and distribute these bacilli in a virulent state 

 for several days. Opportunities for infecting themselves from 

 the bloody discharges of diseased animals probably often occur. 

 Spores of B. anthracis can be carried for longer periods, and 

 flies, which die while containing the spores, remain infective for 

 long periods. Further spores ingested by the larvse are present 

 in the flies which develop from them. The part, if any, played 

 by flies in the spread of this disease has not been ascertained. 



Though evidence is lacking there can be little doubt that the 

 spores of other pathogenic bacilli, such as B. osdematis maligni 

 and B. anthracis symptoviatici, behave in the same way as anthrax 

 spores (Chapter xvii). 



The organisms of other bacterial diseases, especially oph- 

 thalmia, may be distributed in the ways already mentioned, but 

 little definite evidence on the subject is available (Chapter xvill). 



It is also possible that non-biting flies disseminate the virus 

 of certain non-bacterial disease, more especially the Spironcma 

 pertenuis of Yaws (Chapter XIX). 



Experimentally it has been shown that flies can carry and 

 distribute the smaller ova of ' worms ' parasitic in the human 



