I02 



DISTRIBUTION OF BACTERIA 



{/) The influence of various kinds of food on the period 

 during zuhich infected fcecal material is passed. 



As it had previously been found that the rate of deposition 

 of faeces depended to some extent on the kind of food, an 

 experiment was made in order to ascertain whether the period 

 during which the faeces continued infective was influenced by 

 the food. Different batches of flies were allowed to feed for 

 15 minutes on syrup, milk and sputum infected with B. pro- 

 digiosus and then transferred to fresh cages. Every day the 

 cages were changed and the flies fed on non-infected syrup, 

 milk and sputum respectively. The faecal material present in 

 the old cages was emulsified in water and the emulsion was 

 sown on agar. The following table gives the results of these 

 experiments. 



TABLE 12. SJioiving the inflncnee of the food on the 

 infectivity of the fa^ees. 



Cultures from the feces of flies fed on 



This table shows that B. prodigiosus cannot be cultivated 

 from the faeces of flies fed on sputum after 48 hours. It was 

 noticed that the faeces of these flies were much more voluminous 

 than those of the flies fed on milk or syrup. The faeces of the 

 flies fed on milk were infective for 7 days and those of the flies 

 fed on syrup for only 4 days. 



To ascertain how long B. prodigiosus is capable of surviving 

 in various fluids dried on glass, small drops (about the size of 

 the faecal deposits) of the syrup, milk and sputum used to infect 

 the flies and of an emulsion in water were placed on glass and 



