ROBERT S. BREED 



393 



inal conceptions of the two species as emended by the series of papers mentioned 

 above. 



The former author would, however, do away with the name B. acidi lactici and 

 substitute the little-known Bacterium duodenale Ford' which he has included, with B. 

 aerogenes, under Eiicapsitlata with the new name Bacillus duodenale. In placing them 

 among the Eucapsulata, he follows Castellani and Chalmers,^ who include both 

 species in their genus Encapsulatus. Perkins prefers Ford's specific name on the 

 ground that the original description was more definite than that of B. acidi lactici. He 

 feels that later investigators should not emend the original indefinite descriptions even 

 where, as in this case, the principal emendations have been based on the study of ap- 

 parently authentic cultures. Nevertheless, he uses the studies that he made in 1904 to 

 support the view that the original cultures of these organisms were capsulated. More- 

 over, the emendation of species descriptions is permitted under all internationally rec- 

 ognized codes of nomenclature where it is carried out with regard to certain well- 

 established principles. 



Weldin places the two colon organisms in question in separate genera, following 

 Bergey^ in placing Hueppe's organism in the genus Escherichia, and Beijerinck^ in 

 making Escherich's organism the type species of genus Aerobacter, the latter on the 

 ground that this name has priority over Encapsulatus. 



Few systematic studies of the colon group having been made in Continental 

 Europe, it is not surprising to find many of their bacteriologists conservatively taking 

 the position that the two species are identical. Burri and Duggeli,5 however, note the 

 difference in sucrose fermentation as well as other less important differences. 



Pfeiffer's Kapselbacillus [Klebsiella capsulatus (Sternberg) Bergey] is regarded as 

 identical with Aerobacter aerogenes by Castellani and Chalmers, and by Weldin; and 

 the names that have been appHed to this bacterium are included in their lists of syn- 

 onyms of A erohacter aerogenes. 



Analyses of the gases produced, made by more accurate methods than were avail- 

 able to Escherich, have shown that Escherichia acidi lactici produces approximately 

 equal quantities of carbon dioxide and hydrogen, while Aerobacter aerogenes produces 

 at least twice as much carbon dioxide as hydrogen. 



The former has been established as a methyl-red positive, methyl-carbinol nega- 

 tive organism that produces indol readily. It does not form such an abundant slimy 

 growth as the latter, and capsule formation is questioned by some, though it has been 

 noted by Perkins, and by Castellani and Chalmers. 



The latter is methyl-red negative, methyl-carbinol positive, and indol is rarely 

 formed. It forms an abundant, slimy growth, and there is general agreement that the 

 organisms are capsulated. It ferments many of the more complex carbohydrates and 

 alcohols (except dulcitol), usually even attacking starch. It does not Hquefy gelatin, 

 however, as does the closely related Aerobacter cloacae (Jordan) Bergey. 



' Ford, W. W.: Studies froin Roy. Victoria Hosp., Montreal, i. No. 5. Pp. 95. 1903. 

 * Castellani, A., and Chalmers, A. J.: Manual of Tropical Medicine (3d ed.). London, 1919. Ann. 

 de rinst. Pasteur, 34, 600. 1920. 



3 Bergey, D. H.: op. cit. (ist ed.)., Baltimore, 1923. 



-i Beijerinck, M. W.: op. cit., 4, i. 1900; Centralbl. f. Baktcriol., Abt. II, 6, 193. 1900. 



s Burri, R., and Diiggeli, M.: Centralbl./. Baktcriol., Abt. I, Orig., 49, 145. 1909. 



