l62 SUMMER DIARRHCEA 



Altogether 642 flies from diarrhoea infected houses were 

 examined and 600 from non-diarrhoea infected houses. 



Methods. 



'•The flies were caught in balloon traps and examined as soon as possible. The 

 whole trap was placed in a bell-jar and the flies killed by the addition of a few drops 

 of chloroform. For examination each fly was placed on a sterile glass plate and the 

 intestinal canal, including the crop, dissected out with sterile needles. The intestinal 

 contents were emulsified in a small quantity of sterile salt solution. In many cases an 

 emulsion was also made from the external parts of the fly. With the fluids thus 

 obtained plate cultures were made. The medium used for the plates was MacConkey's 

 bile-salt lactose neutral red agar with crystal violet (i — 100,000). The plates were 

 incubated at 37° C. for 48 hours. At the end of this period the plates were examined, 

 and the red lactose fermenting colonies, resembling those produced by bacilli of the 

 colon type, recorded. When non-lactose fermenting colonies were present, sub- 

 cultures were made from three of them in different tubes of litmus lactose peptone 

 water. These cultures were incubated for seven days. If at the end of that time acid 

 had not been produced, cultures were made from these tubes on to agar slopes. After 

 incubation the latter cultures were kept until the further cultural characters of the 

 bacilli could be determined. Previous to testing the fermenting properties, plate 

 cultures on MacConkey's medium were again made in order to test the purity of the 

 cultures. From single colonies on these plates lactose litmus peptone water tubes 

 were inoculated and from them cultures on agar prepared. Thus, every precaution 

 was taken to procure pure cultures before the fluid media were inoculated. 



" In order to test the fermenting properties, six litmus peptone water tubes (each 

 provided with a Durham's tube) containing o'5 per cent, of the following substances, 

 glucose, mannite, dulcite, saccharose, salicin and sorbite, were inoculated. The 

 reactions of all these cultures were recorded on the first, second, third and tenth days 

 of incubation at 37° C. At the same time sub-cultures were also made in milk and 

 in broth and gelatin slopes inoculated. Cultures were examined for motility after 

 24 hours' incubation, and a broth culture was tested for indol on the seventh day. 

 For this purpose the para-dimethyl-amido-benzaldehyde test was used. The gelatin 

 slope cultures were kept at room temperature for a month. They were examined at 

 frequent intervals." 



Classification of bacilli, zvhich do not ferment lactose or 

 liquefy gelatin. 



" Wlien acid production, with or without gas formation, occurred the reaction was 

 usually well marked after 24 to 48 hours' incubation. In some cases, however, several 

 days elapsed before the reaction became definitely acid. It was found that in some 

 cases the formation of acid was followed by a return to alkalinity. In tabulating the 

 results a culture which produced acid at any time was recorded as acid, whether it 

 subsequently became alkaline or not, except in the case of milk cultures. The changes 

 in the latter medium were fully recorded. 



"The writer found great difificuliy in comparing the results of investigators who had 

 recently worked on the non-lactose fermenting bacilli in fixjces, owing to the dift'erent 



