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lished the differences in a striking manner. (1) They failed 

 to grow in all media, if these are incubated at 37 C. ; there 

 was no perceptible growth at this temperature either on agar, 

 or in broth, or in milk. (2) They completely failed to alter 

 MacConkey fluid at 37 C. ; B. typhosus turns it red, but 

 forms no gas. (3) They failed to cause any change in litmus 

 milk ; B. typhosus forms gradually acid (red) without altering 

 the fluid character of the milk. (4) They produced no 

 growth either in neutral red broth or in phenol broth. 



In addition to these differences the microbe grew very 

 slowly on gelatine : it took two to three days before any 

 distinct growth could be noticed, and then it was very trans- 

 parent, unlike that produced by B. typhosus ; and, lastly, in 

 shake gelatine it did not form its colonies in the depth of the 

 medium like the B. typhosus, but, besides being much slower 

 in its growth, it formed colonies only or principally near the 

 free surface of the medium. 



It is therefore clear that this microbe need cause no 

 difficulty in the search for the B. typhosus on Drigalski 

 plates kept at 37 C., being a microbe not capable of growing 

 at that temperature. 



(b.) Of the most frequent "blue" or " violet" colonies found 

 in Drigalski plates inoculated with sewage or faecal matter, 

 with sewage or fsecal matter polluted shellfish oysters, mussels, 

 and cockles are those of streptococci. These appear already 

 after 24 hours at 37 C. ; better and more conspicuously later 

 as violet-blue small round dots, uniformly raised and moist 

 looking. A particle of a colony emulsified and looked at 

 under the microscope is at once recognised as a compound of 

 diplococci and short streptococci. They possess the additional 

 character of staining with gram. Owing to their small size, 

 their violet-blue colour, and their appearance under the 

 microscope, viz., being cocci, they need not further offer any 

 difficulty in respect of being mistaken for anything else. 



(c.) Eepeatedly I have come across in Drigalski. plates at 

 37 C., that had been inoculated with sewage, bright Hue small 

 colonies, more or less conical in shape. They are composed 

 of vibrios or comma bacilli ; they resemble in size, shape, 



