DISSEMINATION OF OPHTHALMIA BY FLIES 275 



flies seventeen hours after they had been contaminated. Ganon 

 (1908) found that flies could transmit infection for at least twenty- 

 four hours after feeding upon infected matter and that during such 

 a period they may be carried long distances in railway carriages. 

 He was unable to show that flies could retain the power of infecting 

 for more than four days, as the experimental flies did not live 

 longer than that time. 



Graham-Smith (1910) has carried on a few experiments on the 

 distribution of the cholera vibrios by flies. Flies were fed for an 

 liour on a cholera culture emulsified in broth, afterwards they were 

 transferred to a fresh cage. At intervals specimens were caught 

 and cultures were made of head, leg, wing, crop, and intestinal 

 contents, the cultures being subsequently plated out and also 

 examined microscopically. The cholera vibrios were found on the 

 legs up to thu'ty hours after infection but not later. They per- 

 sisted in the intestine and crop for forty-eight hours but could not 

 be found after that time. The faeces passed thirty hours after 

 feeding were infected. 



The foregoing experiments prove beyond doubt the ability of 

 flies to carry the cholera organism both internally and externally, 

 in a virulent condition and to infect food for a significant length of 

 time after feeding upon or coming in contact with infected matter. 

 Among those authors who have expressed their belief in the possi- 

 bility of flies acting as agents in the dissemination of cholera, the 

 names of Marpmann (1897) and Geddings (1903) may be men- 

 tioned. 



Ophthalmia. 



Flies are now generally recognised as active and important 

 agents in the spread of ophthalmia, and although, so far as I have 

 been able to discover, we have little bacteriological evidence at 

 present to support this belief, the circumstantial evidence is suffi- 

 ciently strong to warrant it. Nuttall and Jepson (I.e.) point out 

 that Budd as early as 1862 considered it was fully proven that flies 

 serve as carriers of Egyptian ophthalmia. 



In speaking of its occurrence at Biskra, Laveran (1880) says 

 that in the hot season the eyelids of the indigenous children are 

 covered with flies, to the attentions of which they submit ; in this 



18—2 



