300 THE CARRIAGE OF VARIOUS MICRO-ORGANISMS 



Intestinal Protozoa. 



Stiles (1913) in an interesting note refers to the possibility 

 of flies transferring intestinal protozoa such as Entamoeba coli, 

 Lamhlia duodenalis or Trichomonas intestinalis from faecal material 

 to food supplies. He suggests that the presence of such protozoa 

 in food supplies might be taken as an indication of contamination^ 

 The possibility of flies becoming infected, owing to their habits, 

 with intestinal amoebae has also been discussed by Converse 

 (1910) and others. 



In considering experiments on artificially infected flies it 

 should be remembered that the flies are enabled to obtain, in 

 most cases, a much grosser infection than they might be able to 

 obtain under natural conditions. Further, many factors which 

 might possibly aftect the degree of infectivity under natural 

 conditions have not exercised possible adverse influences. Pending 

 the results of further investigations therefore, experiments which 

 have been carried out under unusually favourable artificial condi- 

 tions must be considered in conjunction with those performed 

 under natural conditions, which are chiefly recorded in the accounts 

 given of the various specific diseases. The experiments of Giissow 

 and of Cox, Lewis and Glynn which have been described in this 

 section admirably demonstrate the nature and extent of natural 

 infection. 



1 Stiles and Keister (1913) have investigated this matter further with the result 

 that they have arrived at the conclusion that the evidence that flies commonly 

 act as carriers of the spores of intestinal protozoa is not very conclusive. 



