39 



in the Souta African war the same conditions were present and 

 enteric fever raged; these conditions are well known now; open 

 latrines, frequented by incipient cases of enteric, swarmed with 

 myriads of flies who also haunted the mess tents, defiling the food, 

 and in many cases distinguishable by the lime which they bore on 

 their appendages from the latrines. 



One of the most important and convincing experiments is that 

 of Gussow, who obtained 30 colonies comprising 6 species of bac- 

 teria, and 6 colonies comprising 4 species of fungi, from a single 

 fly caught in a living room and allowed to walk over a culture plate 

 of agar-agar. Flies captured near excremental products generally 

 carry putrefactive bacteria. Hamilton recovered B. typhosus five 

 times in 1 8 experiments from flies caught in two undrained privies 

 and in the room of an -enteric fever patient. 



The habits of these insects are perfectly suited to the dissemi- 

 nation of pathogenic bacteria ; they seek all kind of excrementous 

 and decaying matter for the purpose of depositing their eggs, and 

 fly with perfect freedom on milk, sugar, etc., which form excellent 

 mediums for the deposition of the bacteria they have become con- 

 taminated with. 



Of all substances flies prefer horse-manure for depositing their 

 eggs. The most important factor which affects the number and 

 potential danger of flies is temperature. During the hot months of 

 July, August and September, flies are most abundant and it is sig- 

 nificant that in years when the temperature is high there is almost 

 always a high mortality from typhoid fever during the third quarter 

 of the year, as also from infantile diarrhea. Morgan has disco- 

 vered a bacillus present in a large percentage of cases of the 

 latter disease, which has been isolated from flies captured in in- 

 fected houses. 



The fly problem may be attacked and solved in cities and towns 

 providing the authorities will take the necessary steps. Stable re- 

 fuse should not be left exposed for more than 6 or 7 days in the 

 summer, but should be removed from the vicinity of dwellings, 

 treated with chloride of lime and kept in a closed, flyproof chamber. 



Though the common house-fly usually constitutes from 90 to 

 98 / of the fly population of houses certain other species are also 

 found to occur. The blood-sucking fly which is frequently mistaken 

 for an ordinary fly is found in houses in the spring and autumn. \ 

 Not infrequently inflammatory swellings are caused by the bite of \ 

 one of these flies and they may cause malignant pustule by the 

 mechanical transference of the Bacillus anthracis. 



