W. L. HOLM AN 113 



typhosus B, after it had grown in lactose bouillon for four to six days, prevented the 

 development of gas by B. coli when this was added. Members of the closely related 

 hog-cholera group had no such action in the given time, but after eighteen days' 

 growth they also inhibited the gas production for the B. coli added at this Time. A 

 fuller analysis of this phenomenon is found in an article by Holman and Meekison.' 

 Besson and De Lavergne^ confirmed the results of T. and D. E. Smith and found that 

 B. aertrycki gave the reactions of the hog-cholera group. Brutsaert^ found the phenom- 

 enon most inconstant and variable even in repeated tests of the same strain of bacillus. 

 A hog-cholera type-agglutinating culture inhibited, but as a rule members of this 

 group did not. Moreover, the phenomenon failed if, instead of lactose bouillon, a 

 lactose peptone water were used. He found it too irregular for use in classification. 

 Von Jeney" in studying this question used a bouillon previously freed from glucose by 

 a twenty-four hour growth of beer yeast. (T. and D. E. Smiths presumably used B. 

 coli for this purpose.) Both of these procedures may have an important bearing on 

 the results since the effect of these preliminary cultures may be very great as is seen 

 in many of the articles reviewed above and in the studies of Robertson^ on food ac- 

 cessory factors in bacterial growth. Although such media may not interfere with gas 

 production by the B. coli per se, it may have an effect on the combined metabolism. 

 Von Jeney' investigated the subject very fully. He found five strains of B. para- 

 typhosus B among twenty-six studied which increased the B. coli gas production. Also 

 plates from the mixtures at times gave pure B. coli. The strains of the B. paratypho- 

 siis, isolated from the mixture, did not always give the same results on retest. B, 

 typhosus also inhibited. He searched for any evidence of bacteriophage action, but 

 was only able to discover suggestions of such and no continuous passage was possible. 

 Kauffmann* carried the work further and used besides human strains, as von Jeney 

 had done, a large number of animal strains. He tested thirty different cultures of B. 

 coli and found in pure culture that their gas production was most variable, ranging 

 between o and 100 per cent in twenty-four hours, and for no known reason. He also 

 used yeast-treated media. Some B. coli strains grown from the same stools as strains 

 of B. paratyphosiis showed delayed gas production on glucose, but this was not the 

 rule. On the other side he used thirty human B. paratyphosus B strains, Gaertner's 

 bacillus, B. typhosus, and others and a further group of fifteen strains from animals. 

 Besides the regular tests he used a number of heterologous and homologous combina- 

 tions with the cultures from individual stools. A great irregularity was found through- 

 out. After passage, certain strains of the B. paratyphosus increased in inhibitory 

 powers, but the B. coli did not become more sensitive by such passage. There was, 

 however, no regularity. The animal strains gave the same kind of results as the hu- 

 man. Certain "pseudo-unstable" forms were sometimes seen on plates. In summing 



' Holman, W. L., and Meekison, D. M.: /. Infect. Dis., 39, 145. 1926. 



^ Besson and de Lavergne: Compl. rend. Soc. de biol., 86, 357. 1922. 



3 Brutsaert, P.: ibid., 88, 306. 1923. 



■* von Jeney, A.: loc. cit. s Smith, T., and D. E.: loc. oil. 



^Robertson, R. C: /. Infect. Dis., 34, 395. 1924; 35, 311; 1924. 



' von Jeney, A. : loc. cit. 



* Kauffmann, F.: Zlschr.f. Ilyg. u. Infeklionskrankh., 102, 68. 1924. 



