33 



Theobald Smith, Kligler, Winslow and others have reported that with 

 cultures of Bact. cloacae motility and fermentation of carbohydrates per- 

 sisted after the power to liquefy gelatin had disappeared. Digestion of 

 gelatin is generally considered a reliable differential test. We therefore 

 need have no compunction about utilizing the apparently more persistent 

 fermentation reactions in studies on classification of the colon group. 



Theobald Smith, 1893, suggested that sucrose fermentation may be 

 employed to subdivide the colon group into two subgroups and in 1901 

 Durham suggested the name Bact. coli communior for the sucrose positive 

 variety and noted that the fermentation of starch was distinctive of Bact. 

 lactis aerogenes. 



MacConkey's Classification. In 1905 MacConkey divided lactose 

 fermenting (acid and gas) bacilli into four groups on the basis of fer- 

 mentation of sucrose and dulcitol. 



In 1909 he recognized in each group a number of varieties which were 

 distinguished on the basis of their reactions to the Voges Proskauer test, 

 motility, indol production, gelatin liquefaction, fermentation of inulin 

 adonitol, and inosite. The probable existence of 128 different strains or 

 32 varieties in each of his four subdivisions was suggested. Many of these 

 have been isolated, described, and given specific names. Others have been 

 merely indicated by a number in his classification as shown in Table XVI. 



Bergey and Deehan's Varieties. Very similar to MacConkey's 

 classification is that of Bergey and Deehan (1908). They employed eight 

 characters fermentation of sucrose, dulcitol, adonitol, and inulin; gelatin 

 liquefaction, indol production, motility, and the Vogese Proskauer reaction 

 and from a consideration of all possible combinations recognized the pos- 

 sible existence of 256 varieties. 



The Jackson Classification. In 1911, Jackson proposed a classi- 

 fication resembling that of MacConkey but preference is given to dulcitol 

 over sucrose for the primary division. Each of the four groups thus 

 formed, which are regarded as species, are then further divided on raf- 

 finose and mannitol into four varieties designated (A, B. C, and D), and 

 further differentiation may then be made on motility, indol, gelatin lique- 

 faction, fermentation of other carbohydrates, etc., giving subvarieties, in- 

 dicated by numerical suffixes (A 1? A 2 , B 2 , etc.). This scheme which was 

 included in the Standard Method for a Water Analysis for 1912 is detailed 

 in Table XVII. 



