CHAPTER XXIV 



MISCELLANEOUS EXPERIMENTS ON THE CARRIAGE OF 

 MICRO-ORGANISMS BY FLIES, BY BOTH NATURAL AND 

 ARTIFICIAL INFECTION 



In addition to the experimental evidence which has accumu- 

 lated on the relation of flies to specific diseases, there are also on 

 record a considerable number of experiments on the carriage of 

 various micro-organisms, not in every case pathogenic, by flies. 

 As these experiments have usually some particular interest I have 

 brought together such as seemed worthy of record. 



I have previously recorded (1910) a very interesting series of 

 experiments carried out in 1908 by Glissow. Their particular 

 interest lies in the fact that they clearly demonstrate the varied 

 bacterial and fungal flora which the house^y normally carries. 



Gllssow's experiments were as follows : 



E.rperiment No. 1. 



A fly was caught in his living room (Norwood, London) at 10 a.m. on 

 May 4th and allowed to walk over nutrient agar-agar in a Petri dish ; the 

 necessary precautions being taken to prevent extraneous infection of the 

 medium. The Petri dish was placed in an incubator and kept at 28 — 30° C. 

 At 6 p.m. on the same day there were plain indications of colonies forming, 

 but they were too small to allow a separation count. 



May 5th, 10 a.m. 7 colonies of bacteria and 4 of fungi showing. 

 „ 6th, 10 a.m. 16 „ „ 5 „ 



„ 7th, 10 a.m. 23 „ „ 6 „ 



„ 8th, 10 a.m. 30 „ „ 6 „ 



That i.s, in 96 hours, 30 colonies of bacteria and 6 colonies of fungi were 

 observed. 



The fungi were examined and identified as follows : 

 2 colonies of Saccharomyces sp. 

 2 „ Penicillmm ylaucum 



1 colony of Aspergillus niger 

 1 „ Cladosporium herbanim 



