OTHER BACTERIAL DISEASES 1 89 



of any importance. Yersin (1894) and Nuttall (1897) have, 

 however, both shown that when opportunities for infection occur 

 flies may contain living and virulent plague {B. pestis) bacilli for 

 at least 48 hours after infection. 



StapJiylococcal infections. 



Staphylococci of various kinds have been isolated from the 

 external parts and from the alimentary canal of the fly by 

 various observers, and there can be little doubt that flies can 

 carry these organisms from the pus in which they occur to open 

 sores on healthy individuals. 



CHAPTER XIX 



NON-BACTERIAL DISEASES 



Infantile paralysis or acnte anterior poliomyelitis. 



Though the precise nature of the virus of this disease has 

 not been demonstrated, Flexner and his colleagues and other 

 observers have shown that it is present in the throat and nose 

 and also sometimes in the intestinal discharges. Flies can, there- 

 fore, often gain access to infectious material, and Flexner and 

 Clark (19 11) and Howard and Clark (19 12) have investigated the 

 subject experimentally. Some experiments by the latter observers 

 are quoted. 



" After being allowed to feed on infected cord the flies {M. dotnestica) were placed 

 in fresh receptacles from which certain numbers were removed at intervals, killed with 

 ether, ground up with sand in physiological salt solution, and passed through a 

 Berkefeld filter. The filtrate was injected as usual into the brain of Macacus rhesus 

 monkeys." One monkey {A) received "3 c.c. of a filtrate of the bodies of 7 flies 

 which had had an opportunity to feed on infected cord for 5 hours, and had then lived 

 in clean surroundings for 24 hours before they were killed." On the sixth day the 

 monkey became weak and showed typical symptoms of the disease on the eighth 

 day, when it was killed. "At autopsy the cord showed the characteristic macroscopic 

 lesions of experimental poliomyelitis. The microscopic sections were also typical." 

 Another monkey {B) which had received " 4 c.c. of the filtrate of the bodies of 

 10 flies which had fed on infected cord 48 hours previously," showed marked symptoms 

 on the twelfth day and was killed. " The autopsy showed characteristic lesions of 

 experimental poliomyelitis in the spinal cord, and the sections typical histological 



