75 



It appears to me that Durham's statement seems to rely, 

 besides the morphological characters of the microbe in ques- 

 tion, chiefly on the fact that it produces alkali in litmus 

 milk. But this will barely be considered a sufficient reason, 

 since, in the first place, other alkali-producing microbes do 

 the same, and, in the second place, the manner of the alkali 

 production is distinctly different for the B. fsecalis and the 

 B. Gaertner. If the B. fsecalis is planted in litmus milk, 

 and this is kept at 37 C., it will be noticed that the litmus 

 milk from the outset becomes more and more blue, whereas 

 with the B. Gaertner under the same conditions the litmus 

 milk for the first 24-48 hours shows a tinge of redness, that 

 is, slight acid production, and this gradually gives way to a 

 change into slate colour and later into deep blue. It 

 requires only sub-cultures in glucose gelatine, in MacConkey 

 fluid and in neutral red broth to establish marked differences, 

 for, as mentioned on a former page : 

 B. Gaertner turns neutral red broth greenish fluorescent ; 



MacConkey fluid red, and forms slowly gas 



therein ; 



ferments glucose gelatine, forming gas therein ; 

 whereas the action of the B. faecalis is in these respects 

 quite negative. 



The presence of blue colonies looking like those of 

 B. typhosus or B. Gaertner, composed of motile cylindrical 

 bacilli, and answering to the tests characteristic of 

 the B. fsecalis (alkaligenes), is therefore of an im- 

 portant diagnostic value, inasmuch as they have not been 

 at present found in any but human excremental matter ; 

 unfortunately, their occurrence in highly diluted 'matter, 

 such as is employed for making a Drigalski plate, is 

 rather rare, but if present it is of so much greater im- 

 portance. 



On a former page we mentioned an experiment (IX) in 

 which one lot of Dutch oysters were placed in sewage 

 polluted sea water, the other lot being kept in sterile sea 

 water for control. After 24 hours one oyster of each lot, as 

 described in Experiment IX, was analysed by Drigalski 



