•292 •iiiK wATKU-si'rri.v of towns in tiii; ■ntoi-R-s 



coiiimiiiiin ' to a group of organisms, or even so-called varioties, and (2) The tests laid down 

 as essential according to the definitions quoted, do not go far enough ; that the list contains 

 too many that arc of doubtful significance and utility, and too few that are admittedly 

 of greater importance in the identification of a bacillus. To discuss this last objection 

 first : Houston, Savage, and all experienced bacteriologists admit that the tests given above 

 are not of equal value in the identification of what they term ' coli.' Thus, to quote from 

 Conipaiaiivo Savage, ' Ditferent characters have not an equal value. Some, such as the fermentation of 

 sugars, liquefaction of gelatine, and acid production in milk are of so permanent a type that 

 for an isolated organism to show divergence from a typical Bacillus coli iu any one of these 

 particulars would be to throw grave doubt on its being excretal at all, while others, such as 

 the gelatine surface colonies, and the exhibition of motility, are so subject to variation that 

 comparatively little significance can be attached to their, perhaps temporary, absence 

 or modification.' And again in another place he says : ' Organisms that differ from the 

 typical excretal type (bacillus coli coinniiinit:) only in the fact that they show no motility and 

 that their gelatine colonies are atypical, may be regarded as not having their significance 

 diminished on these grounds. Similarly, the loss of indol-production power would not 

 reduce their significance very markedly. On the other hand the absence of glucose 

 or lactose fermentation would at once, in the writer's opinion, exclude the organism isolated 

 from being bacillus coli at all.' " 



The obvious inference from these opinions is, why not do away with some of these 

 doubtful tests, and substitute for them the more important fermentation reactions in sugars 

 such as dulcite, adonite and iuulin ? These are entirely on a parallel with the glucose and 

 lactose fermentation referred to as being " of a permanent character." This is practically 

 the position taken up by MacConkey in his paper on the Bacteriology of Milk {Journal of 

 llijgienc, Vol. IV., No. 3, July, 1906), and, following his reconniiendations, by ourselves 

 in the work under report. 



He proceeds to illustrate his argument by the results obtained by the application of the 

 proposed methods to Indian waters. It is found that Houston's true li. coli can be split up 

 into ten different bacilli, while if his non-typical coli is also considered, more are added 

 to the list, a list which includes B. (jrunfhal, B. oxijtncus perniciosvf, B. coscoroba and others, 

 distinguished so far only by numbers.* According to Clemesha the definitions of Houston 

 and Savage err in omission as well as in commission. He says: "Take the organism 

 li.cliMct hacilliis cloacm as an example: it will be observed that this organism does not come within 



Houston's definition of ' true coli,' because it ferments saccharose, nor within Savage's 

 group that indicates fiecal contamination, because it liquefies gelatine, yet it is undoubtedly 

 fajcal in origin. Why should the mere fact that this organism liquefies gelatine mean 

 that it does not indicate fiEcal contamination to an equal extent as any non-liquefier "? 

 Surely, considering it originally came from the fieces of man or some other animal, the 

 coincidence that it liquefies gelatine cannot put it beyond the range of indicators of faical 

 contamination. As a matter of fact B. cloacae is not an indicator of daiujerous and recent 

 pollution, because it is a resistant organism with a fondness for the bottom of lakes, and 

 river sand; but the liquefaction of gelatine has nothing to do with these facts," and 

 continues : 



"The weak point of the above method lies in the statement that a large number of 

 what we believe to be entirely different species of bacilli eiiuallij represent danyerous fxcal 

 contamination. If this be so, it should be demonstrable that these different species are 



• For list aud tables, sec Captaiu Archibald's paper, p. 319 



