278 THE DISSEMINATION OF OTHER DISEASES BY FLIES 



Abel cites Welander (1896) who describes the infection of a woman 

 in a hospital. This patient's bed was next to that of another 

 patient suffering from blennorrhoea, but a screen which did not 

 reach to the ceiling separated the two beds. All means of infection, 

 except through the agency of flies, appeared to be excluded. 

 Welander found that flies bore living gonococci upon their feet 

 three hours after they had been contaminated with secretion. 



Plague. 



Althiaigh fleas are considered to be the chief agents in the 

 dissemination of the plague bacillus, in spite of the fact that 

 the proof is not as yet considered by all to be absolutely con- 

 vincing, it is nevertheless interesting from an historical point of 

 view to refer to the ideas that have prevailed and the experiments 

 which have been carried out in reference to the relation of flies to 

 plague. Nuttall and Jepson (1909) refer to the earlier writings 

 on this subject. The prevalence of large numbers of flies during 

 outbreaks of plague has been referred to by Knud as early as 1498 

 and by Varwich in 1577. Mercurialis (1577) referred to the con- 

 tamination of food by flies which had been frequenting plague 

 patients. The infection of healthy persons by contaminated flies 

 was also suggested by Lange (1791). Haesar (1882) is cited by 

 the above authors as refening to Bengasi, Tripolis, where an 

 epidemic of plague occurred in 1858, being known to the Turks 

 by the name of the " Kingdom of Flies." 



Yersin (1894) observed the presence of dead flies in the 

 laboratory in w^hich autopsies on plague animals were made. He 

 demonstrated the presence of virulent plague bacilli in such dead 

 flies by inoculation experiments. Nuttall (1897) conclusively 

 proved that flies were able to carry the plague bacillus and that 

 they subsequently died of the disease. The flies were fed on 

 organs of animals which had died of plague. He found that such 

 flies might survive eight days at 12—14° C. and that they still 

 contained the virulent bacilli for forty-eight hours or more after 

 they were transferred to clean vessels. At temperatures of 1 4° C. 

 and higher, the infected flies died more quickly than did the 

 control flies which had been fed on the organs of healthy animals. 



