788 



SCIENCE 



[N. S. Vol. XXXIX. No. 1013 



On account of the conservatism of tlie 

 author, great interest attaches to such state- 

 ments as he makes concerning actual danger 

 from flies. He shows that infected flies not 

 only carry bacteria on their bodies and limbs, 

 thereby contaminating substances over which 

 they walk, but distribute bacteria which they 

 have ingested, by means of vomit and fecal 

 deposits. He shows that, while non-spore- 

 bearing bacteria survive at the most only 

 twenty-four hours on the limbs, flies never- 

 theless infect substances over which they walk 

 with such organisms for several days by means 

 of a fluid which they regurgitate from their 

 crops. He also shows that the majority of the 

 non-spore-bearing bacilli pass through the 

 intestine and are in living condition in the 

 fecal deposits. He states that flies feeding 

 upon tubercular sputum sufl^er from diarrhea, 

 a fact which may be of some importance in 

 relation to their potentiality for spreading 

 infection. He states that city flies carry in 

 and on their bodies very large numbers of 

 bacteria, many of which are fecal types and 

 that these are more numerous in flies caught 

 in congested or dirty areas. Pathogenic bac- 

 teria or allied types have been isolated from 

 wild city flies. " Flies bred from larvae living 

 in material infected with anthrax spores are 

 capable of communicating the disease for 

 some days after they emerge." 



He admits that the evidence is very strong 

 that flies are the dominating factor in the dis- 

 semination of typhoid fever in military and 

 other camps and in stations in the tropics, and 

 that there is some evidence that they are 

 factors in causing the autumnal increase 

 in typhoid in England, but agrees with 

 Chapin that it is unlikely that they play an 

 important part in well-sewered towns. The 

 evidence in epidemic diarrhea of children he 

 thinks is not altogether conclusive, largely I 

 imagine because, although the disease is ad- 

 mittedly infectious, the causative organism 

 has not been identified with certainty. He 

 considers that 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 exhibit- 

 ing a high mortality, though expensive, would 

 be justified." It is interesting to note that 

 this is just what was done last summer in New 

 York City by Dr. Donald B. Armstrong, of 

 the Bureau of Public Health and Hygiene of 

 the New York Association for Improving the 

 Condition of the Poor, with results that are 

 convincing, and Levy of Richmond, in an ad- 

 dress as yet unpublished, states that he has 

 reduced the mortality from infantile diarrhea 

 in Eichmond more than fifty per cent, by anti- 

 fly work and great care to protect the diapers 

 of sick children from flies. Armstrong's ex- 

 periment, by the way, was accompanied by a 

 rigid control. 



With regard to cholera, he states that the 

 evidence concerning its spread by flies is some- 

 what old, but is so remarkable that careful in- 

 vestigation is highly desirable. 



Admitting that flies are greatly attracted to 

 tuberculous sputum and can carry and dis- 

 tribute Bacillus tuberculosis for several days, 

 he contends that whether they are serious 

 factors in the spread of the disease remains to 

 be proved. 



Concerning the organisms of other bacterial 

 diseases, especially ophthalmia, he states that 

 these may be distributed by flies, but little 

 definite evidence on the subject is available. 



It is surely not the intention of Dr. 

 Graham-Smith to underestimate the danger 

 from flies, although his book read by the un- 

 scientific eye may produce this effect on the 

 unscientific mind. He closes with a strong 

 plea for careful additional observations and 

 investigations. For the elucidation of some 

 of the problems, while expert knowledge is re- 

 quired, he states that accurate observations 

 by workers without especial scientific train- 

 ing will be of the greatest assistance. 



The book as a whole is an excellent one. I 

 wish that the writer might have displayed 

 more of the arguments against flies that are 

 not founded upon definite bacteriological 

 examinations; but there are other books that 

 do that, and this one is a reliable one to have 



