DISSEMINATION OF DIPHTHERIA KV FLIES 279 



In two of the experiments the infected flies were all dead on the 

 seventh and eighth days respectively at temperatures of 14" C. 

 These facts indicate that flies shoidd not be allowed to have 

 access to the bodies or excreta of cases of plague or to the food. 



Small-pox. 



Nuttall and Jepson (I.e.) give one reference only to flies in 

 relation to small-pox. Hervieux (1904) states that Laforgue at 

 Tamorna-Djedida, Province of Constantine, observed that during 

 an epidemic of small-pox at that place all the children who were 

 attacked lived in the south-west of the village and there was no 

 small-pox in the northern part of the village. This distribution 

 of the disease was attributed to the direction of the prevailing 

 winds, and observations indicated that flies and mosquitoes were 

 distributed with the wind. Laforgue believed that flies played an 

 important part in spreading the virus of small-pox. 



Diphtheria. 



While it is hardly likely, as Nuttall and Jepson have pointed 

 out, that under natural conditions flies would play any part in 

 the dissemination of diphtheria, it is conceivable that, if the 

 necessary conditions of infection occurred they would carry the 

 infection. Dickenson (1907) cites Smith (1898) who carried out 

 the usual and hardly valuable experiment of allowing flies to walk 

 over infected matter and afterwards over culture media, with the 

 natural positive results. The unreliable character of such experi- 

 ments is indicated by the results of the experiments which Graham- 

 Smith (1910) carried out with Bacillus diphtheriae. Two series 

 of experiments were made. In the first flies were allowed to feed 

 for thirty minutes on an emulsion of B. diphtheriae in saliva and 

 then transferred to a fresh cage. At intervals from one hour up 

 to seventy-two hours after feeding flies were killed and cultures 

 w^ere made on transparent serum medium fi'om their legs, wings, 

 heads, crops and intestinal contents. In the second series of 

 experiments the flies were allowed to feed for one hour on an 

 emulsion of B. diphtheriae in broth and afterwards they were 

 treated similarly to the flies in the first series. From the 



