DISTRIBUTION OF BACTERIA 



Methods. 



Small numbers of flies were used and kept in the glass cages which have been 

 alluded to (Chapter VIII). Infected material (usually an emulsion of B. prodigiosus in 

 syrup) was only supplied to them for 15 minutes or less, and the cages were changed 

 daily. In prolonged experiments they were fed, every day, with plain syrup or other 

 food. For cultural purposes two or three flies were caught in a large test-tube and 

 killed by chloroform vapour. The legs, wings, and heads were cut ofif and separately 

 inoculated on different parts of an agar plate. In many caSes fluid was also expressed 

 from the proboscis by means of pressure on the head and separately cultivated. The 

 body, after being placed in alcohol, or singed in the flame, was dissected, under a 

 Zeiss binocular microscope, and the contents of the crop and intestines separately 

 inoculated. The mounted Hagedorn needles and other instruments used for dissection 

 were sterilized in the flame. After a little experience it is not difficult to dissect out 

 the entire crop and sow its contents, and to subsequently remove the intestine without 

 contamination with the crop contents. The agar plates on which the cultures were 

 generally made were prepared and dried for a few minutes in the incubator at 37° C, 

 and the legs, wings, head, and crop, and intestinal contents, etc. from one fly inoculated 

 at difterent places. The spots where the crop and intestinal contents had been placed 

 were marked by blue rings made with a glass pencil on the back of the plate, and 

 when, as was often found possible, the organs of several flies were inoculated on one 

 plate, those belonging to each fly were surrounded by a blue line and numbered. 



Plate XX, fig. I, illustrates a plate, before cultivation, in- 

 oculated with the organs of four flies infected with anthrax. 

 Figure 2 shows the same plate after 24 hours' incubation. 



{a) Experiments on the duration of life of B. prodigios?is on the 

 exterior, and in the alimentary canal of flies. 



The following table summarizes the results of four series of 

 experiments, done at different times, on the length of life of 

 B. prodigiosus on the feet and wings, and in the alimentary canal. 

 In each case syrup infected with B. prodigiosus was placed for a 

 few minutes in a cage containing hungry flies. After feeding, 

 the flies were transferred to fresh cages, where, if the experiment 

 was prolonged, they were fed daily with plain syrup. At intervals, 

 specimens were caught and dissected, and their legs, wings, 

 heads, and the contents of their crops and intestines inoculated 

 on to agar plates. 



