BACILLUS PEODIGIOSUS AND POLIOMYELITIS 293 



In 1907 experiments were carried out by Dr M. B. Arnold 

 and myself with B. prodigiosus. Flies which had just emerged 

 from the pupae, and therefore not already contaminated with an 

 extensive bacterial flora, were allowed to walk over a film of the 

 bacillus, after which they were confined to sterile glass tubes. At 

 varying periods they were taken out and allowed to walk over the 

 culture plates. Those contained for over twelve hours retained 

 the bacillus on their appendages and transferred them subse- 

 quently to the culture media, but they were not recovered from 

 those flies which were kept in confinement for twenty-four hours ; 

 a large number of flies, however, were not used. 



In discussing the relation of flies to typhoid fever reference v/as 

 made to the infection of milk. In this connection an interesting 

 investigation was made by Esten and Mason (1908) on the role 

 which flics play in the carriage of bacteria to milk. 



The flies were caught by means of a sterile net ; they were 

 then introduced into a sterile bottle and shaken up in a known 

 quantity of sterilised water to wash the bacteria from their bodies 

 and to simulate the number of organisms that would come from 

 a fly falling into a quantity of milk. They summarised their 

 results in the table given on the opposite page. 



While the counts of the bacteria can only be considered as 

 comparative the results indicate clearly the nature of the source 

 of infection. Commenting on these results the authors state that 

 " early in the fly season the numbers of bacteria are comparatively 

 large. The place where flies live also determine largely the 

 numbers they carry." 



Polioinyelitis. 



Experiments have been carried on and are being continued by 

 Flexner and Clarke (1911) on the contamination of the house-fly 

 with the virus of poliomyelitis, more generally known as infantile 

 paralysis or spinal meningitis. It was found that flies contaminated 

 with the virus of poliomyelitis harboured the virus in a living and 

 infectious state for at least forty-eight hours. It was not shown 

 that this is the limit of the period of survival and the experiments 

 threw no light on the question as to whether the virus is retained 

 merely as a superficial contamination or whether it could survive 



