698 SHIGELLA 



Wheeler (1944o, h), however, agrees with Boyd in this matter. The gas-producing, 

 dulcitol-positive, indole-negative Newcastle bacillus, is sufficiently distinctive to 

 justify the award of specific rank. Its possession of the group Flexner antigen 

 is no more a reason for including it in th.QJiexneri species than the common possession 

 of a group antigen between Sh. alkalescens and Boyd's strain P274 is sufficient 

 to justify ranking these two biochemically distinct organisms in the same species. 

 On the whole, we would accept Boyd's general thesis, but would prefer to accord 

 specific rank to the Newcastle bacillus, and to delay the final numbering of the 

 flexneri types till the position of X is cleared up. 



When we come to consider the definition of the hoyd species, we are again in 

 difficulties, because we know far too little as yet to decide what strains to place 

 in it. Provisionally, we may accept Type 170 as hoyd i, P288 as hoyd ii, Dl as 

 hoyd iii, and P274 as hoyd iv, but until the species can be properly defined, we are 

 on very unsure ground. 



In the lactose-fermenting subdivision of the mannitol-fermenting group, Sh. 

 dispar ferments xylose and sorbitol, produces indole, and is generally M.R. -f-, 

 while Sh. sonnei is negative in all these respects. Sonne's bacillus appears to be 

 antigenically homogeneous, and to differ from Sh. dispar, which is antigenically 

 heterogeneous. In contrast to most other workers, Bojlen (1934), who has made a 

 study of Sonne dysentery in Denmark, maintains that many strains ferment xylose. 

 He divides the Sonne group into six sub-groups on the basis of maltose and xylose 

 fermentation. Maltose fermentation is admitted to be irregular, except with freshly 

 isolated strains, and two of the sub-groups are differentiated from two of the others 

 merely by their slightly delayed fermentation of certain sugars. The justification 

 advanced for such a procedure is that in any given closed epidemic the strains 

 isolated belonged to one sub-group. It is very doubtful whether, in the absence 

 of other correlated properties, attention should be paid by systematists to minor 

 fermentative activities that may be characteristic of strain rather than of type 

 differences. The fact, moreover, that xylose-positive strains of Sonne appear to 

 be uncommon outside of Denmark suggests that Bojlen's classification should be 

 accepted with reserve until it has received confirmation from other countries. 



There is in the lactose-fermenting sub-group an undefined series of strains 

 usually referred to by the term Bad. coU anaerogenes. Some of these strains are 

 undoubtedly of the Sonne or dispar type (see Nabarro 1923, 1927 ; Koser et al. 

 1930). Others are distinguished from these organisms by the fact that they produce 

 small quantities of gas, often late, in glucose, maltose, mannitol, sucrose, or salicin, 

 maltose being one of the commonest. Organisms of this type are not infrequently 

 found in milk (Wilson et al. 1935), and appear to be related more nearly to the 

 coli-eerogenes than to the dysentery group. Some anaerogenes strains are motile, 

 and some liquefy gelatin. 



Nomenclature.— The old practice of regarding all dysentery bacilli as belonging 

 to a single species, Bad. dysenterice, has clearly nothing to support it. If the 

 numerous differences between the Shiga, Flexner, and Sonne bacillus are insufficient 

 to justify the award to each of specific rank, then it is impossible to decide on 

 what grounds species should ever be separated. Just as much reason exists for 

 classifying the colon and the typhoid bacillus in a single species as for uniting 

 the Shiga and the Sonne bacillus. In the second edition of this book we adopted 

 the expedient of classifying the dysentery bacilli in the genus Baderium and 

 awarding them the specific names of shigce, flexneri, and sonnei, etc. There is 



